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</div><hr /><div id="language.types.array" class="sect1">
<h2 class="title">Arrays</h2>
<p class="para">
An <span class="type"><a href="language.types.array.html" class="type array">array</a></span> in PHP is actually an ordered map. A map is a type that
associates <em class="emphasis">values</em> to <em class="emphasis">keys</em>. This type
is optimized for several different uses; it can be treated as an array,
list (vector), hash table (an implementation of a map), dictionary,
collection, stack, queue, and probably more. As <span class="type"><a href="language.types.array.html" class="type array">array</a></span> values can
be other <span class="type"><a href="language.types.array.html" class="type array">array</a></span>s, trees and multidimensional <span class="type"><a href="language.types.array.html" class="type array">array</a></span>s
are also possible.
</p>
<p class="para">
Explanation of those data structures is beyond the scope of this manual, but
at least one example is provided for each of them. For more information, look
towards the considerable literature that exists about this broad topic.
</p>
<div class="sect2" id="language.types.array.syntax">
<h3 class="title">Syntax</h3>
<div class="sect3" id="language.types.array.syntax.array-func">
<h4 class="title">Specifying with <span class="function"><a href="function.array.html" class="function">array()</a></span></h4>
<p class="para">
An <span class="type"><a href="language.types.array.html" class="type array">array</a></span> can be created using the <span class="function"><a href="function.array.html" class="function">array()</a></span>
language construct. It takes any number of comma-separated
<em><span class="replaceable">key</span> => <span class="replaceable">value</span></em> pairs
as arguments.
</p>
<pre class="synopsis">
array(
<span class="optional"><span class="replaceable">key</span> => </span><span class="replaceable">value</span>,
<span class="optional"><span class="replaceable">key2</span> => </span><span class="replaceable">value2</span>,
<span class="optional"><span class="replaceable">key3</span> => </span><span class="replaceable">value3</span>,
...
)</pre>
<p class="para">
The comma after the last array element is optional and can be omitted. This is usually done
for single-line arrays, i.e. <em>array(1, 2)</em> is preferred over
<em>array(1, 2, )</em>. For multi-line arrays on the other hand the trailing comma
is commonly used, as it allows easier addition of new elements at the end.
</p>
<p class="para">
As of PHP 5.4 you can also use the short array syntax, which replaces
<em>array()</em> with <em>[]</em>.
</p>
<div class="example" id="example-83">
<p><strong>Example #1 A simple array</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(<br /> </span><span style="color: #DD0000">"foo" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"bar" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"foo"</span><span style="color: #007700">,<br />);<br /><br /></span><span style="color: #FF8000">// as of PHP 5.4<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= [<br /> </span><span style="color: #DD0000">"foo" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"bar" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"foo"</span><span style="color: #007700">,<br />];<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
The <span class="replaceable">key</span> can either be an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
or a <span class="type"><a href="language.types.string.html" class="type string">string</a></span>. The <span class="replaceable">value</span> can be
of any type.
</p>
<p class="para">
Additionally the following <span class="replaceable">key</span> casts will occur:
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
<span class="type"><a href="language.types.string.html" class="type String">String</a></span>s containing valid <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>s will be cast to the
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> type. E.g. the key <em>"8"</em> will actually be
stored under <em>8</em>. On the other hand <em>"08"</em> will
not be cast, as it isn't a valid decimal integer.
</span>
</li>
<li class="listitem">
<span class="simpara">
<span class="type"><a href="language.types.float.html" class="type Float">Float</a></span>s are also cast to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>s, which means that the
fractional part will be truncated. E.g. the key <em>8.7</em> will actually
be stored under <em>8</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
<span class="type"><a href="language.types.boolean.html" class="type Bool">Bool</a></span>s are cast to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>s, too, i.e. the key
<em>true</em> will actually be stored under <em>1</em>
and the key <em>false</em> under <em>0</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
<span class="type"><a href="language.types.null.html" class="type Null">Null</a></span> will be cast to the empty string, i.e. the key
<em>null</em> will actually be stored under <em>""</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
<span class="type"><a href="language.types.array.html" class="type Array">Array</a></span>s and <span class="type"><a href="language.types.object.html" class="type object">object</a></span>s <em class="emphasis">can not</em> be used as keys.
Doing so will result in a warning: <em>Illegal offset type</em>.
</span>
</li>
</ul>
</p>
<p class="para">
If multiple elements in the array declaration use the same key, only the last one
will be used as all others are overwritten.
</p>
<div class="example" id="example-84">
<p><strong>Example #2 Type Casting and Overwriting example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(<br /> </span><span style="color: #0000BB">1 </span><span style="color: #007700">=> </span><span style="color: #DD0000">"a"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"1" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"b"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">1.5 </span><span style="color: #007700">=> </span><span style="color: #DD0000">"c"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">true </span><span style="color: #007700">=> </span><span style="color: #DD0000">"d"</span><span style="color: #007700">,<br />);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(1) {
[1]=>
string(1) "d"
}
</pre></div>
</div>
<div class="example-contents"><p>
As all the keys in the above example are cast to <em>1</em>, the value will be overwritten
on every new element and the last assigned value <em>"d"</em> is the only one left over.
</p></div>
</div>
<p class="para">
PHP arrays can contain <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> and <span class="type"><a href="language.types.string.html" class="type string">string</a></span> keys at the same time
as PHP does not distinguish between indexed and associative arrays.
</p>
<div class="example" id="example-85">
<p><strong>Example #3 Mixed <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> and <span class="type"><a href="language.types.string.html" class="type string">string</a></span> keys</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(<br /> </span><span style="color: #DD0000">"foo" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"bar" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"foo"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">100 </span><span style="color: #007700">=> -</span><span style="color: #0000BB">100</span><span style="color: #007700">,<br /> -</span><span style="color: #0000BB">100 </span><span style="color: #007700">=> </span><span style="color: #0000BB">100</span><span style="color: #007700">,<br />);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
["foo"]=>
string(3) "bar"
["bar"]=>
string(3) "foo"
[100]=>
int(-100)
[-100]=>
int(100)
}
</pre></div>
</div>
</div>
<p class="para">
The <span class="replaceable">key</span> is optional. If it is not specified, PHP will
use the increment of the largest previously used <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> key.
</p>
<div class="example" id="example-86">
<p><strong>Example #4 Indexed arrays without key</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"foo"</span><span style="color: #007700">, </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">, </span><span style="color: #DD0000">"hallo"</span><span style="color: #007700">, </span><span style="color: #DD0000">"world"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
[0]=>
string(3) "foo"
[1]=>
string(3) "bar"
[2]=>
string(5) "hallo"
[3]=>
string(5) "world"
}
</pre></div>
</div>
</div>
<p class="para">
It is possible to specify the key only for some elements and leave it out for others:
</p>
<div class="example" id="example-87">
<p><strong>Example #5 Keys not on all elements</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(<br /> </span><span style="color: #DD0000">"a"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"b"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">6 </span><span style="color: #007700">=> </span><span style="color: #DD0000">"c"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"d"</span><span style="color: #007700">,<br />);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[6]=>
string(1) "c"
[7]=>
string(1) "d"
}
</pre></div>
</div>
<div class="example-contents"><p>
As you can see the last value <em>"d"</em> was assigned the key
<em>7</em>. This is because the largest integer key before that
was <em>6</em>.
</p></div>
</div>
</div>
<div class="sect3" id="language.types.array.syntax.accessing">
<h4 class="title">Accessing array elements with square bracket syntax</h4>
<p class="para">
Array elements can be accessed using the <em>array[key]</em> syntax.
</p>
<div class="example" id="example-88">
<p><strong>Example #6 Accessing array elements</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= array(<br /> </span><span style="color: #DD0000">"foo" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"bar"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">42 </span><span style="color: #007700">=> </span><span style="color: #0000BB">24</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"multi" </span><span style="color: #007700">=> array(<br /> </span><span style="color: #DD0000">"dimensional" </span><span style="color: #007700">=> array(<br /> </span><span style="color: #DD0000">"array" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"foo"<br /> </span><span style="color: #007700">)<br /> )<br />);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #DD0000">"foo"</span><span style="color: #007700">]);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #0000BB">42</span><span style="color: #007700">]);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #DD0000">"multi"</span><span style="color: #007700">][</span><span style="color: #DD0000">"dimensional"</span><span style="color: #007700">][</span><span style="color: #DD0000">"array"</span><span style="color: #007700">]);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
string(3) "bar"
int(24)
string(3) "foo"
</pre></div>
</div>
</div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Both square brackets and curly braces can be used interchangeably
for accessing array elements (e.g. $array[42] and $array{42} will
both do the same thing in the example above).
</p>
</p></blockquote>
<p class="para">
As of PHP 5.4 it is possible to array dereference the result of a function
or method call directly. Before it was only possible using a temporary
variable.
</p>
<p class="para">
As of PHP 5.5 it is possible to array dereference an array literal.
</p>
<div class="example" id="example-89">
<p><strong>Example #7 Array dereferencing</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">getArray</span><span style="color: #007700">() {<br /> return array(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #FF8000">// on PHP 5.4<br /></span><span style="color: #0000BB">$secondElement </span><span style="color: #007700">= </span><span style="color: #0000BB">getArray</span><span style="color: #007700">()[</span><span style="color: #0000BB">1</span><span style="color: #007700">];<br /><br /></span><span style="color: #FF8000">// previously<br /></span><span style="color: #0000BB">$tmp </span><span style="color: #007700">= </span><span style="color: #0000BB">getArray</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$secondElement </span><span style="color: #007700">= </span><span style="color: #0000BB">$tmp</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">];<br /><br /></span><span style="color: #FF8000">// or<br /></span><span style="color: #007700">list(, </span><span style="color: #0000BB">$secondElement</span><span style="color: #007700">) = </span><span style="color: #0000BB">getArray</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Attempting to access an array key which has not been defined is
the same as accessing any other undefined variable:
an <strong><code>E_NOTICE</code></strong>-level error message will be
issued, and the result will be <strong><code>NULL</code></strong>.
</p>
</p></blockquote>
</div>
<div class="sect3" id="language.types.array.syntax.modifying">
<h4 class="title">Creating/modifying with square bracket syntax</h4>
<p class="para">
An existing <span class="type"><a href="language.types.array.html" class="type array">array</a></span> can be modified by explicitly setting values
in it.
</p>
<p class="para">
This is done by assigning values to the <span class="type"><a href="language.types.array.html" class="type array">array</a></span>, specifying the
key in brackets. The key can also be omitted, resulting in an empty pair of
brackets (<em>[]</em>).
</p>
<pre class="synopsis">
$arr[<span class="replaceable">key</span>] = <span class="replaceable">value</span>;
$arr[] = <span class="replaceable">value</span>;
// <span class="replaceable">key</span> may be an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> or <span class="type"><a href="language.types.string.html" class="type string">string</a></span>
// <span class="replaceable">value</span> may be any value of any type</pre>
<p class="para">
If <var class="varname"><var class="varname">$arr</var></var> doesn't exist yet, it will be created, so this is
also an alternative way to create an <span class="type"><a href="language.types.array.html" class="type array">array</a></span>. This practice is
however discouraged because if <var class="varname"><var class="varname">$arr</var></var> already contains
some value (e.g. <span class="type"><a href="language.types.string.html" class="type string">string</a></span> from request variable) then this
value will stay in the place and <em>[]</em> may actually stand
for <a href="language.types.string.html#language.types.string.substr" class="link">string access
operator</a>. It is always better to initialize variable by a direct
assignment.
</p>
<p class="para">
To change a certain
value, assign a new value to that element using its key. To remove a
key/value pair, call the <span class="function"><a href="function.unset.html" class="function">unset()</a></span> function on it.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$arr </span><span style="color: #007700">= array(</span><span style="color: #0000BB">5 </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">12 </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$arr</span><span style="color: #007700">[] = </span><span style="color: #0000BB">56</span><span style="color: #007700">; </span><span style="color: #FF8000">// This is the same as $arr[13] = 56;<br /> // at this point of the script<br /><br /></span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">"x"</span><span style="color: #007700">] = </span><span style="color: #0000BB">42</span><span style="color: #007700">; </span><span style="color: #FF8000">// This adds a new element to<br /> // the array with key "x"<br /> <br /></span><span style="color: #007700">unset(</span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">5</span><span style="color: #007700">]); </span><span style="color: #FF8000">// This removes the element from the array<br /><br /></span><span style="color: #007700">unset(</span><span style="color: #0000BB">$arr</span><span style="color: #007700">); </span><span style="color: #FF8000">// This deletes the whole array<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
As mentioned above, if no key is specified, the maximum of the existing
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> indices is taken, and the new key will be that maximum
value plus 1 (but at least 0). If no <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> indices exist yet, the key will
be <em>0</em> (zero).
</p>
<p class="para">
Note that the maximum integer key used for this <em class="emphasis">need not
currently exist in the <span class="type"><a href="language.types.array.html" class="type array">array</a></span></em>. It need only have
existed in the <span class="type"><a href="language.types.array.html" class="type array">array</a></span> at some time since the last time the
<span class="type"><a href="language.types.array.html" class="type array">array</a></span> was re-indexed. The following example illustrates:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Create a simple array.<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= array(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">, </span><span style="color: #0000BB">4</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Now delete every item, but leave the array itself intact:<br /></span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$array </span><span style="color: #007700">as </span><span style="color: #0000BB">$i </span><span style="color: #007700">=> </span><span style="color: #0000BB">$value</span><span style="color: #007700">) {<br /> unset(</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #0000BB">$i</span><span style="color: #007700">]);<br />}<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Append an item (note that the new key is 5, instead of 0).<br /></span><span style="color: #0000BB">$array</span><span style="color: #007700">[] = </span><span style="color: #0000BB">6</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Re-index:<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= </span><span style="color: #0000BB">array_values</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$array</span><span style="color: #007700">[] = </span><span style="color: #0000BB">7</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<p class="para">The above example will output:</p>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)
Array
(
)
Array
(
[5] => 6
)
Array
(
[0] => 6
[1] => 7
)
</pre></div>
</div>
</div>
</p></blockquote>
</div>
</div>
<div class="sect2" id="language.types.array.useful-funcs">
<h3 class="title">Useful functions</h3>
<p class="para">
There are quite a few useful functions for working with arrays. See the
<a href="ref.array.html" class="link">array functions</a> section.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
The <span class="function"><a href="function.unset.html" class="function">unset()</a></span> function allows removing keys from an
<span class="type"><a href="language.types.array.html" class="type array">array</a></span>. Be aware that the array will <em class="emphasis">not</em> be
reindexed. If a true "remove and shift" behavior is desired, the
<span class="type"><a href="language.types.array.html" class="type array">array</a></span> can be reindexed using the
<span class="function"><a href="function.array-values.html" class="function">array_values()</a></span> function.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$a </span><span style="color: #007700">= array(</span><span style="color: #0000BB">1 </span><span style="color: #007700">=> </span><span style="color: #DD0000">'one'</span><span style="color: #007700">, </span><span style="color: #0000BB">2 </span><span style="color: #007700">=> </span><span style="color: #DD0000">'two'</span><span style="color: #007700">, </span><span style="color: #0000BB">3 </span><span style="color: #007700">=> </span><span style="color: #DD0000">'three'</span><span style="color: #007700">);<br />unset(</span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">]);<br /></span><span style="color: #FF8000">/* will produce an array that would have been defined as<br /> $a = array(1 => 'one', 3 => 'three');<br /> and NOT<br /> $a = array(1 => 'one', 2 =>'three');<br />*/<br /><br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">array_values</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">// Now $b is array(0 => 'one', 1 =>'three')<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p></blockquote>
<p class="para">
The <a href="control-structures.foreach.html" class="link">foreach</a> control
structure exists specifically for <span class="type"><a href="language.types.array.html" class="type array">array</a></span>s. It provides an easy
way to traverse an <span class="type"><a href="language.types.array.html" class="type array">array</a></span>.
</p>
</div>
<div class="sect2" id="language.types.array.donts">
<h3 class="title">Array do's and don'ts</h3>
<div class="sect3" id="language.types.array.foo-bar">
<h4 class="title">Why is <em>$foo[bar]</em> wrong?</h4>
<p class="para">
Always use quotes around a string literal array index. For example,
<em>$foo['bar']</em> is correct, while
<em>$foo[bar]</em> is not. But why? It is common to encounter this
kind of syntax in old scripts:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$foo</span><span style="color: #007700">[</span><span style="color: #0000BB">bar</span><span style="color: #007700">] = </span><span style="color: #DD0000">'enemy'</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">$foo</span><span style="color: #007700">[</span><span style="color: #0000BB">bar</span><span style="color: #007700">];<br /></span><span style="color: #FF8000">// etc<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
This is wrong, but it works. The reason is that this code has an undefined
constant (bar) rather than a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> ('bar' - notice the
quotes). PHP may in the future define constants which, unfortunately for such
code, have the same name. It works because PHP automatically converts a
<em class="emphasis">bare string</em> (an unquoted <span class="type"><a href="language.types.string.html" class="type string">string</a></span> which does
not correspond to any known symbol) into a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> which
contains the bare <span class="type"><a href="language.types.string.html" class="type string">string</a></span>. For instance, if there is no defined
constant named <strong><code>bar</code></strong>, then PHP will substitute in the
<span class="type"><a href="language.types.string.html" class="type string">string</a></span> <em>'bar'</em> and use that.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
This does not mean to <em class="emphasis">always</em> quote the key. Do not
quote keys which are <a href="language.constants.html" class="link">constants</a> or
<a href="language.variables.html" class="link">variables</a>, as this will prevent
PHP from interpreting them.
</span>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />error_reporting</span><span style="color: #007700">(</span><span style="color: #0000BB">E_ALL</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">ini_set</span><span style="color: #007700">(</span><span style="color: #DD0000">'display_errors'</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">ini_set</span><span style="color: #007700">(</span><span style="color: #DD0000">'html_errors'</span><span style="color: #007700">, </span><span style="color: #0000BB">false</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">// Simple array:<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= array(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$count </span><span style="color: #007700">= </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br />for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700">< </span><span style="color: #0000BB">$count</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700">++) {<br /> echo </span><span style="color: #DD0000">"\nChecking </span><span style="color: #0000BB">$i</span><span style="color: #DD0000">: \n"</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">"Bad: " </span><span style="color: #007700">. </span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #DD0000">'$i'</span><span style="color: #007700">] . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">"Good: " </span><span style="color: #007700">. </span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #0000BB">$i</span><span style="color: #007700">] . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">"Bad: </span><span style="color: #007700">{</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #DD0000">'$i'</span><span style="color: #007700">]}</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br /> echo </span><span style="color: #DD0000">"Good: </span><span style="color: #007700">{</span><span style="color: #0000BB">$array</span><span style="color: #007700">[</span><span style="color: #0000BB">$i</span><span style="color: #007700">]}</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">The above example will output:</p>
<div class="example-contents screen">
<div class="cdata"><pre>
Checking 0:
Notice: Undefined index: $i in /path/to/script.html on line 9
Bad:
Good: 1
Notice: Undefined index: $i in /path/to/script.html on line 11
Bad:
Good: 1
Checking 1:
Notice: Undefined index: $i in /path/to/script.html on line 9
Bad:
Good: 2
Notice: Undefined index: $i in /path/to/script.html on line 11
Bad:
Good: 2
</pre></div>
</div>
</p></blockquote>
<p class="para">
More examples to demonstrate this behaviour:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Show all errors<br /></span><span style="color: #0000BB">error_reporting</span><span style="color: #007700">(</span><span style="color: #0000BB">E_ALL</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$arr </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'fruit' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'apple'</span><span style="color: #007700">, </span><span style="color: #DD0000">'veggie' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'carrot'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Correct<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'fruit'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// apple<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'veggie'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// carrot<br /><br />// Incorrect. This works but also throws a PHP error of level E_NOTICE because<br />// of an undefined constant named fruit<br />// <br />// Notice: Use of undefined constant fruit - assumed 'fruit' in...<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">fruit</span><span style="color: #007700">]; </span><span style="color: #FF8000">// apple<br /><br />// This defines a constant to demonstrate what's going on. The value 'veggie'<br />// is assigned to a constant named fruit.<br /></span><span style="color: #0000BB">define</span><span style="color: #007700">(</span><span style="color: #DD0000">'fruit'</span><span style="color: #007700">, </span><span style="color: #DD0000">'veggie'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Notice the difference now<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'fruit'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// apple<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">fruit</span><span style="color: #007700">]; </span><span style="color: #FF8000">// carrot<br /><br />// The following is okay, as it's inside a string. Constants are not looked for<br />// within strings, so no E_NOTICE occurs here<br /></span><span style="color: #007700">print </span><span style="color: #DD0000">"Hello </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">fruit</span><span style="color: #007700">]</span><span style="color: #DD0000">"</span><span style="color: #007700">; </span><span style="color: #FF8000">// Hello apple<br /><br />// With one exception: braces surrounding arrays within strings allows constants<br />// to be interpreted<br /></span><span style="color: #007700">print </span><span style="color: #DD0000">"Hello </span><span style="color: #007700">{</span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">fruit</span><span style="color: #007700">]}</span><span style="color: #DD0000">"</span><span style="color: #007700">; </span><span style="color: #FF8000">// Hello carrot<br /></span><span style="color: #007700">print </span><span style="color: #DD0000">"Hello </span><span style="color: #007700">{</span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'fruit'</span><span style="color: #007700">]}</span><span style="color: #DD0000">"</span><span style="color: #007700">; </span><span style="color: #FF8000">// Hello apple<br /><br />// This will not work, and will result in a parse error, such as:<br />// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'<br />// This of course applies to using superglobals in strings as well<br /></span><span style="color: #007700">print </span><span style="color: #DD0000">"Hello </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'fruit']"</span><span style="color: #007700">;<br />print </span><span style="color: #DD0000">"Hello </span><span style="color: #0000BB">$_GET</span><span style="color: #007700">[</span><span style="color: #DD0000">'foo']"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Concatenation is another option<br /></span><span style="color: #007700">print </span><span style="color: #DD0000">"Hello " </span><span style="color: #007700">. </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #DD0000">'fruit'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// Hello apple<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
When <a href="errorfunc.configuration.html#ini.error-reporting" class="link">error_reporting</a> is set to
show <strong><code>E_NOTICE</code></strong> level errors (by setting it to
<strong><code>E_ALL</code></strong>, for example), such uses will become immediately
visible. By default,
<a href="errorfunc.configuration.html#ini.error-reporting" class="link">error_reporting</a> is set not to
show notices.
</p>
<p class="para">
As stated in the <a href="language.types.array.html#language.types.array.syntax" class="link">syntax</a>
section, what's inside the square brackets ('<em>[</em>' and
'<em>]</em>') must be an expression. This means that code like
this works:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$arr</span><span style="color: #007700">[</span><span style="color: #0000BB">somefunc</span><span style="color: #007700">(</span><span style="color: #0000BB">$bar</span><span style="color: #007700">)];<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
This is an example of using a function return value as the array index. PHP
also knows about constants:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_ERROR</span><span style="color: #007700">] = </span><span style="color: #DD0000">"A fatal error has occurred"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_WARNING</span><span style="color: #007700">] = </span><span style="color: #DD0000">"PHP issued a warning"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_NOTICE</span><span style="color: #007700">] = </span><span style="color: #DD0000">"This is just an informal notice"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
Note that <strong><code>E_ERROR</code></strong> is also a valid identifier, just like
<em>bar</em> in the first example. But the last example is in fact
the same as writing:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">] = </span><span style="color: #DD0000">"A fatal error has occurred"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">] = </span><span style="color: #DD0000">"PHP issued a warning"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">8</span><span style="color: #007700">] = </span><span style="color: #DD0000">"This is just an informal notice"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
because <strong><code>E_ERROR</code></strong> equals <em>1</em>, etc.
</p>
<div class="sect4" id="language.types.array.foo-bar.why">
<h5 class="title">So why is it bad then?</h5>
<p class="para">
At some point in the future, the PHP team might want to add another
constant or keyword, or a constant in other code may interfere. For
example, it is already wrong to use the words <em>empty</em> and
<em>default</em> this way, since they are
<a href="reserved.html" class="link">reserved keywords</a>.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
To reiterate, inside a double-quoted <span class="type"><a href="language.types.string.html" class="type string">string</a></span>, it's valid to
not surround array indexes with quotes so <em>"$foo[bar]"</em>
is valid. See the above examples for details on why as well as the section
on <a href="language.types.string.html#language.types.string.parsing" class="link">variable parsing in
strings</a>.
</span>
</p></blockquote>
</div>
</div>
</div>
<div class="sect2" id="language.types.array.casting">
<h3 class="title">Converting to array</h3>
<p class="para">
For any of the types: <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, <span class="type"><a href="language.types.float.html" class="type float">float</a></span>,
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>, <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> and <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span>,
converting a value to an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> results in an array with a single
element with index zero and the value of the scalar which was converted. In
other words, <em>(array)$scalarValue</em> is exactly the same as
<em>array($scalarValue)</em>.
</p>
<p class="para">
If an <span class="type"><a href="language.types.object.html" class="type object">object</a></span> is converted to an <span class="type"><a href="language.types.array.html" class="type array">array</a></span>, the result
is an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> whose elements are the <span class="type"><a href="language.types.object.html" class="type object">object</a></span>'s
properties. The keys are the member variable names, with a few notable
exceptions: integer properties are unaccessible;
private variables have the class name prepended to the variable
name; protected variables have a '*' prepended to the variable name. These
prepended values have null bytes on either side. This can result in some
unexpected behaviour:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">class </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> private </span><span style="color: #0000BB">$A</span><span style="color: #007700">; </span><span style="color: #FF8000">// This will become '\0A\0A'<br /></span><span style="color: #007700">}<br /><br />class </span><span style="color: #0000BB">B </span><span style="color: #007700">extends </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> private </span><span style="color: #0000BB">$A</span><span style="color: #007700">; </span><span style="color: #FF8000">// This will become '\0B\0A'<br /> </span><span style="color: #007700">public </span><span style="color: #0000BB">$AA</span><span style="color: #007700">; </span><span style="color: #FF8000">// This will become 'AA'<br /></span><span style="color: #007700">}<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((array) new </span><span style="color: #0000BB">B</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
The above will appear to have two keys named 'AA', although one of them is
actually named '\0A\0A'.
</p>
<p class="para">
Converting <strong><code>NULL</code></strong> to an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> results in an empty
<span class="type"><a href="language.types.array.html" class="type array">array</a></span>.
</p>
</div>
<div class="sect2" id="language.types.array.comparing">
<h3 class="title">Comparing</h3>
<p class="para">
It is possible to compare arrays with the <span class="function"><a href="function.array-diff.html" class="function">array_diff()</a></span>
function and with
<a href="language.operators.array.html" class="link">array operators</a>.
</p>
</div>
<div class="sect2" id="language.types.array.examples">
<h3 class="title">Examples</h3>
<p class="para">
The array type in PHP is very versatile. Here are some examples:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// This:<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= array( </span><span style="color: #DD0000">'color' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'red'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'taste' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'sweet'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'shape' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'round'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'name' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'apple'</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">4 </span><span style="color: #FF8000">// key will be 0<br /> </span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'a'</span><span style="color: #007700">, </span><span style="color: #DD0000">'b'</span><span style="color: #007700">, </span><span style="color: #DD0000">'c'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// . . .is completely equivalent with this:<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= array();<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'color'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'red'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'taste'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'sweet'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'shape'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'round'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'name'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'apple'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[] = </span><span style="color: #0000BB">4</span><span style="color: #007700">; </span><span style="color: #FF8000">// key will be 0<br /><br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= array();<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[] = </span><span style="color: #DD0000">'a'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[] = </span><span style="color: #DD0000">'b'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[] = </span><span style="color: #DD0000">'c'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// After the above code is executed, $a will be the array<br />// array('color' => 'red', 'taste' => 'sweet', 'shape' => 'round', <br />// 'name' => 'apple', 0 => 4), and $b will be the array <br />// array(0 => 'a', 1 => 'b', 2 => 'c'), or simply array('a', 'b', 'c').<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-90">
<p><strong>Example #8 Using array()</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Array as (property-)map<br /></span><span style="color: #0000BB">$map </span><span style="color: #007700">= array( </span><span style="color: #DD0000">'version' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'OS' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'Linux'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'lang' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'english'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'short_tags' </span><span style="color: #007700">=> </span><span style="color: #0000BB">true<br /> </span><span style="color: #007700">);<br /> <br /></span><span style="color: #FF8000">// strictly numerical keys<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= array( </span><span style="color: #0000BB">7</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">8</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">0</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">156</span><span style="color: #007700">,<br /> -</span><span style="color: #0000BB">10<br /> </span><span style="color: #007700">);<br /></span><span style="color: #FF8000">// this is the same as array(0 => 7, 1 => 8, ...)<br /><br /></span><span style="color: #0000BB">$switching </span><span style="color: #007700">= array( </span><span style="color: #0000BB">10</span><span style="color: #007700">, </span><span style="color: #FF8000">// key = 0<br /> </span><span style="color: #0000BB">5 </span><span style="color: #007700">=> </span><span style="color: #0000BB">6</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">3 </span><span style="color: #007700">=> </span><span style="color: #0000BB">7</span><span style="color: #007700">, <br /> </span><span style="color: #DD0000">'a' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">11</span><span style="color: #007700">, </span><span style="color: #FF8000">// key = 6 (maximum of integer-indices was 5)<br /> </span><span style="color: #DD0000">'8' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #FF8000">// key = 8 (integer!)<br /> </span><span style="color: #DD0000">'02' </span><span style="color: #007700">=> </span><span style="color: #0000BB">77</span><span style="color: #007700">, </span><span style="color: #FF8000">// key = '02'<br /> </span><span style="color: #0000BB">0 </span><span style="color: #007700">=> </span><span style="color: #0000BB">12 </span><span style="color: #FF8000">// the value 10 will be overwritten by 12<br /> </span><span style="color: #007700">);<br /> <br /></span><span style="color: #FF8000">// empty array<br /></span><span style="color: #0000BB">$empty </span><span style="color: #007700">= array(); <br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="language.types.array.examples.loop">
<p><strong>Example #9 Collection</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$colors </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'red'</span><span style="color: #007700">, </span><span style="color: #DD0000">'blue'</span><span style="color: #007700">, </span><span style="color: #DD0000">'green'</span><span style="color: #007700">, </span><span style="color: #DD0000">'yellow'</span><span style="color: #007700">);<br /><br />foreach (</span><span style="color: #0000BB">$colors </span><span style="color: #007700">as </span><span style="color: #0000BB">$color</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"Do you like </span><span style="color: #0000BB">$color</span><span style="color: #DD0000">?\n"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Do you like red?
Do you like blue?
Do you like green?
Do you like yellow?
</pre></div>
</div>
</div>
<p class="para">
Changing the values of the <span class="type"><a href="language.types.array.html" class="type array">array</a></span> directly is possible since PHP
5 by passing them by reference. Before that, a workaround is necessary:
</p>
<div class="example" id="language.types.array.examples.changeloop">
<p><strong>Example #10 Changing element in the loop</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// PHP 5<br /></span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$colors </span><span style="color: #007700">as &</span><span style="color: #0000BB">$color</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$color </span><span style="color: #007700">= </span><span style="color: #0000BB">strtoupper</span><span style="color: #007700">(</span><span style="color: #0000BB">$color</span><span style="color: #007700">);<br />}<br />unset(</span><span style="color: #0000BB">$color</span><span style="color: #007700">); </span><span style="color: #FF8000">/* ensure that following writes to<br />$color will not modify the last array element */<br /><br />// Workaround for older versions<br /></span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$colors </span><span style="color: #007700">as </span><span style="color: #0000BB">$key </span><span style="color: #007700">=> </span><span style="color: #0000BB">$color</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$colors</span><span style="color: #007700">[</span><span style="color: #0000BB">$key</span><span style="color: #007700">] = </span><span style="color: #0000BB">strtoupper</span><span style="color: #007700">(</span><span style="color: #0000BB">$color</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$colors</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[0] => RED
[1] => BLUE
[2] => GREEN
[3] => YELLOW
)
</pre></div>
</div>
</div>
<p class="para">
This example creates a one-based array.
</p>
<div class="example" id="example-93">
<p><strong>Example #11 One-based index</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$firstquarter </span><span style="color: #007700">= array(</span><span style="color: #0000BB">1 </span><span style="color: #007700">=> </span><span style="color: #DD0000">'January'</span><span style="color: #007700">, </span><span style="color: #DD0000">'February'</span><span style="color: #007700">, </span><span style="color: #DD0000">'March'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$firstquarter</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[1] => 'January'
[2] => 'February'
[3] => 'March'
)
</pre></div>
</div>
</div>
<div class="example" id="example-94">
<p><strong>Example #12 Filling an array</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// fill an array with all items from a directory<br /></span><span style="color: #0000BB">$handle </span><span style="color: #007700">= </span><span style="color: #0000BB">opendir</span><span style="color: #007700">(</span><span style="color: #DD0000">'.'</span><span style="color: #007700">);<br />while (</span><span style="color: #0000BB">false </span><span style="color: #007700">!== (</span><span style="color: #0000BB">$file </span><span style="color: #007700">= </span><span style="color: #0000BB">readdir</span><span style="color: #007700">(</span><span style="color: #0000BB">$handle</span><span style="color: #007700">))) {<br /> </span><span style="color: #0000BB">$files</span><span style="color: #007700">[] = </span><span style="color: #0000BB">$file</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">closedir</span><span style="color: #007700">(</span><span style="color: #0000BB">$handle</span><span style="color: #007700">); <br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
<span class="type"><a href="language.types.array.html" class="type Array">Array</a></span>s are ordered. The order can be changed using various
sorting functions. See the <a href="ref.array.html" class="link">array functions</a>
section for more information. The <span class="function"><a href="function.count.html" class="function">count()</a></span> function can be
used to count the number of items in an <span class="type"><a href="language.types.array.html" class="type array">array</a></span>.
</p>
<div class="example" id="example-95">
<p><strong>Example #13 Sorting an array</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />sort</span><span style="color: #007700">(</span><span style="color: #0000BB">$files</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$files</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
Because the value of an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> can be anything, it can also be
another <span class="type"><a href="language.types.array.html" class="type array">array</a></span>. This enables the creation of recursive and
multi-dimensional <span class="type"><a href="language.types.array.html" class="type array">array</a></span>s.
</p>
<div class="example" id="example-96">
<p><strong>Example #14 Recursive and multi-dimensional arrays</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$fruits </span><span style="color: #007700">= array ( </span><span style="color: #DD0000">"fruits" </span><span style="color: #007700">=> array ( </span><span style="color: #DD0000">"a" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"orange"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"b" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"banana"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"c" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"apple"<br /> </span><span style="color: #007700">),<br /> </span><span style="color: #DD0000">"numbers" </span><span style="color: #007700">=> array ( </span><span style="color: #0000BB">1</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">2</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">3</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">4</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">5</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">6<br /> </span><span style="color: #007700">),<br /> </span><span style="color: #DD0000">"holes" </span><span style="color: #007700">=> array ( </span><span style="color: #DD0000">"first"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">5 </span><span style="color: #007700">=> </span><span style="color: #DD0000">"second"</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"third"<br /> </span><span style="color: #007700">)<br /> );<br /><br /></span><span style="color: #FF8000">// Some examples to address values in the array above <br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$fruits</span><span style="color: #007700">[</span><span style="color: #DD0000">"holes"</span><span style="color: #007700">][</span><span style="color: #0000BB">5</span><span style="color: #007700">]; </span><span style="color: #FF8000">// prints "second"<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$fruits</span><span style="color: #007700">[</span><span style="color: #DD0000">"fruits"</span><span style="color: #007700">][</span><span style="color: #DD0000">"a"</span><span style="color: #007700">]; </span><span style="color: #FF8000">// prints "orange"<br /></span><span style="color: #007700">unset(</span><span style="color: #0000BB">$fruits</span><span style="color: #007700">[</span><span style="color: #DD0000">"holes"</span><span style="color: #007700">][</span><span style="color: #0000BB">0</span><span style="color: #007700">]); </span><span style="color: #FF8000">// remove "first"<br /><br />// Create a new multi-dimensional array<br /></span><span style="color: #0000BB">$juices</span><span style="color: #007700">[</span><span style="color: #DD0000">"apple"</span><span style="color: #007700">][</span><span style="color: #DD0000">"green"</span><span style="color: #007700">] = </span><span style="color: #DD0000">"good"</span><span style="color: #007700">; <br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
<span class="type"><a href="language.types.array.html" class="type Array">Array</a></span> assignment always involves value copying. Use the
<a href="language.operators.html" class="link">reference operator</a> to copy an
<span class="type"><a href="language.types.array.html" class="type array">array</a></span> by reference.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$arr1 </span><span style="color: #007700">= array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$arr2 </span><span style="color: #007700">= </span><span style="color: #0000BB">$arr1</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$arr2</span><span style="color: #007700">[] = </span><span style="color: #0000BB">4</span><span style="color: #007700">; </span><span style="color: #FF8000">// $arr2 is changed,<br /> // $arr1 is still array(2, 3)<br /> <br /></span><span style="color: #0000BB">$arr3 </span><span style="color: #007700">= &</span><span style="color: #0000BB">$arr1</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$arr3</span><span style="color: #007700">[] = </span><span style="color: #0000BB">4</span><span style="color: #007700">; </span><span style="color: #FF8000">// now $arr1 and $arr3 are the same<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
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