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<title>Integers</title>
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</div><hr /><div id="language.types.integer" class="sect1">
<h2 class="title">Integers</h2>
<p class="simpara">
An <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> is a number of the set
ℤ = {..., -2, -1, 0, 1, 2, ...}.
</p>
<p class="para">
See also:
</p>
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
<a href="book.gmp.html" class="link">Arbitrary length integer / GMP</a>
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="language.types.float.html" class="link">Floating point numbers</a>
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="book.bc.html" class="link">Arbitrary precision / BCMath</a>
</span>
</li>
</ul>
<div class="sect2" id="language.types.integer.syntax">
<h3 class="title">Syntax</h3>
<p class="simpara">
<span class="type"><a href="language.types.integer.html" class="type Integer">Integer</a></span>s can be specified in decimal (base 10), hexadecimal
(base 16), octal (base 8) or binary (base 2) notation.
The <a href="language.operators.arithmetic.html" class="link">negation operator</a>
can be used to denote a negative <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>.
</p>
<p class="para">
Binary <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> literals are available since PHP 5.4.0.
</p>
<p class="para">
To use octal notation, precede the number with a <em>0</em> (zero).
To use hexadecimal notation precede the number with <em>0x</em>.
To use binary notation precede the number with <em>0b</em>.
</p>
<div class="example" id="example-41">
<p><strong>Example #1 Integer literals</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$a </span><span style="color: #007700">= </span><span style="color: #0000BB">1234</span><span style="color: #007700">; </span><span style="color: #FF8000">// decimal number<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= -</span><span style="color: #0000BB">123</span><span style="color: #007700">; </span><span style="color: #FF8000">// a negative number<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= </span><span style="color: #0000BB">0123</span><span style="color: #007700">; </span><span style="color: #FF8000">// octal number (equivalent to 83 decimal)<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= </span><span style="color: #0000BB">0x1A</span><span style="color: #007700">; </span><span style="color: #FF8000">// hexadecimal number (equivalent to 26 decimal)<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= </span><span style="color: #0000BB">0b11111111</span><span style="color: #007700">; </span><span style="color: #FF8000">// binary number (equivalent to 255 decimal)<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
Formally, the structure for <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> literals is:
</p>
<div class="informalexample">
<div class="example-contents">
<div class="cdata"><pre>
decimal : [1-9][0-9]*
| 0
hexadecimal : 0[xX][0-9a-fA-F]+
octal : 0[0-7]+
binary : 0[bB][01]+
integer : decimal
| hexadecimal
| octal
| binary
</pre></div>
</div>
</div>
<p class="para">
The size of an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> is platform-dependent, although a maximum
value of about two billion is the usual value (that's 32 bits signed).
64-bit platforms usually have a maximum value of about 9E18, except on
Windows prior to PHP 7, where it was always 32 bit. PHP does not support
unsigned <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>s. <span class="type"><a href="language.types.integer.html" class="type Integer">Integer</a></span> size can be determined
using the constant <strong><code>PHP_INT_SIZE</code></strong>, maximum value using
the constant <strong><code>PHP_INT_MAX</code></strong> since PHP 5.0.5,
and minimum value using the constant <strong><code>PHP_INT_MIN</code></strong> since
PHP 7.0.0.
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
Prior to PHP 7, if an invalid digit was given in an octal <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
(i.e. 8 or 9), the rest of the number was ignored. Since PHP 7, a parse error
is emitted.
</p>
</div>
</div>
<div class="sect2" id="language.types.integer.overflow">
<h3 class="title">Integer overflow</h3>
<p class="para">
If PHP encounters a number beyond the bounds of the <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
type, it will be interpreted as a <span class="type"><a href="language.types.float.html" class="type float">float</a></span> instead. Also, an
operation which results in a number beyond the bounds of the
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> type will return a <span class="type"><a href="language.types.float.html" class="type float">float</a></span> instead.
</p>
<div class="example" id="example-42">
<p><strong>Example #2 Integer overflow on a 32-bit system</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">2147483647</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// int(2147483647)<br /><br /></span><span style="color: #0000BB">$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">2147483648</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// float(2147483648)<br /><br /></span><span style="color: #0000BB">$million </span><span style="color: #007700">= </span><span style="color: #0000BB">1000000</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">50000 </span><span style="color: #007700">* </span><span style="color: #0000BB">$million</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// float(50000000000)<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-43">
<p><strong>Example #3 Integer overflow on a 64-bit system</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">9223372036854775807</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// int(9223372036854775807)<br /><br /></span><span style="color: #0000BB">$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">9223372036854775808</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// float(9.2233720368548E+18)<br /><br /></span><span style="color: #0000BB">$million </span><span style="color: #007700">= </span><span style="color: #0000BB">1000000</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$large_number </span><span style="color: #007700">= </span><span style="color: #0000BB">50000000000000 </span><span style="color: #007700">* </span><span style="color: #0000BB">$million</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$large_number</span><span style="color: #007700">); </span><span style="color: #FF8000">// float(5.0E+19)<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
There is no <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> division operator in PHP.
<em>1/2</em> yields the <span class="type"><a href="language.types.float.html" class="type float">float</a></span> <em>0.5</em>.
The value can be casted to an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> to round it towards zero, or
the <span class="function"><a href="function.round.html" class="function">round()</a></span> function provides finer control over rounding.
</p>
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">25</span><span style="color: #007700">/</span><span style="color: #0000BB">7</span><span style="color: #007700">); </span><span style="color: #FF8000">// float(3.5714285714286)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((int) (</span><span style="color: #0000BB">25</span><span style="color: #007700">/</span><span style="color: #0000BB">7</span><span style="color: #007700">)); </span><span style="color: #FF8000">// int(3)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">25</span><span style="color: #007700">/</span><span style="color: #0000BB">7</span><span style="color: #007700">)); </span><span style="color: #FF8000">// float(4)<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
<div class="sect2" id="language.types.integer.casting">
<h3 class="title">Converting to integer</h3>
<p class="simpara">
To explicitly convert a value to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, use either the
<em>(int)</em> or <em>(integer)</em> casts. However, in
most cases the cast is not needed, since a value will be automatically
converted if an operator, function or control structure requires an
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> argument. A value can also be converted to
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> with the <span class="function"><a href="function.intval.html" class="function">intval()</a></span> function.
</p>
<p class="simpara">
If a <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> is converted to an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, then
the result will be the unique resource number assigned to the
<span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> by PHP at runtime.
</p>
<p class="simpara">
See also <a href="language.types.type-juggling.html" class="link">Type Juggling</a>.
</p>
<div class="sect3" id="language.types.integer.casting.from-boolean">
<h4 class="title">From <a href="language.types.boolean.html" class="link">booleans</a></h4>
<p class="simpara">
<strong><code>FALSE</code></strong> will yield <em>0</em> (zero), and <strong><code>TRUE</code></strong> will yield
<em>1</em> (one).
</p>
</div>
<div class="sect3" id="language.types.integer.casting.from-float">
<h4 class="title">
From <a href="language.types.float.html" class="link">floating point numbers</a>
</h4>
<p class="simpara">
When converting from <span class="type"><a href="language.types.float.html" class="type float">float</a></span> to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, the number
will be rounded <em class="emphasis">towards zero</em>.
</p>
<p class="para">
If the float is beyond the boundaries of <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> (usually
<em>+/- 2.15e+9 = 2^31</em> on 32-bit platforms and
<em>+/- 9.22e+18 = 2^63</em> on 64-bit platforms other than
Windows), the result is undefined, since the <span class="type"><a href="language.types.float.html" class="type float">float</a></span> doesn't
have enough precision to give an exact <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> result. No
warning, not even a notice will be issued when this happens!
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
As of PHP 7.0.0, instead of being undefined and platform-dependent, NaN and Infinity will
always be zero when cast to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>.
</p>
</p></blockquote>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
Never cast an unknown fraction to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, as this can
sometimes lead to unexpected results.
</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 (int) ( (</span><span style="color: #0000BB">0.1</span><span style="color: #007700">+</span><span style="color: #0000BB">0.7</span><span style="color: #007700">) * </span><span style="color: #0000BB">10 </span><span style="color: #007700">); </span><span style="color: #FF8000">// echoes 7!<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
See also the <a href="language.types.float.html#warn.float-precision" class="link">warning about float
precision</a>.
</p>
</div>
</div>
<div class="sect3" id="language.types.integer.casting.from-string">
<h4 class="title">From strings</h4>
<p class="simpara">
See <a href="language.types.string.html#language.types.string.conversion" class="link">String conversion to
numbers</a>
</p>
</div>
<div class="sect3" id="language.types.integer.casting-from-null">
<h4 class="title">From <span class="type"><a href="language.types.null.html" class="type NULL">NULL</a></span></h4>
<p class="simpara">
<strong><code>NULL</code></strong> is always converted to zero (<em>0</em>).
</p>
</div>
<div class="sect3" id="language.types.integer.casting.from-other">
<h4 class="title">From other types</h4>
<div class="caution"><strong class="caution">Caution</strong>
<p class="simpara">
The behaviour of converting to <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> is undefined for other
types. Do <em class="emphasis">not</em> rely on any observed behaviour, as it
can change without notice.
</p>
</div>
</div>
</div>
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