<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Filters elements of an array using a callback function</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.array-fill.html">array_fill</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.array-flip.html">array_flip</a></div>
<div class="up"><a href="ref.array.html">Array Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.array-filter" class="refentry">
<div class="refnamediv">
<h1 class="refname">array_filter</h1>
<p class="verinfo">(PHP 4 >= 4.0.6, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">array_filter</span> — <span class="dc-title">Filters elements of an array using a callback function</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.array-filter-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">array</span> <span class="methodname"><strong>array_filter</strong></span>
( <span class="methodparam"><span class="type">array</span> <code class="parameter">$array</code></span>
[, <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$flag</code><span class="initializer"> = 0</span></span>
]] )</div>
<p class="para rdfs-comment">
Iterates over each value in the <code class="parameter">array</code>
passing them to the <code class="parameter">callback</code> function.
If the <code class="parameter">callback</code> function returns true, the
current value from <code class="parameter">array</code> is returned into
the result array. Array keys are preserved.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.array-filter-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">array</code></dt>
<dd>
<p class="para">
The array to iterate over
</p>
</dd>
<dt>
<code class="parameter">callback</code></dt>
<dd>
<p class="para">
The callback function to use
</p>
<p class="para">
If no <code class="parameter">callback</code> is supplied, all entries of
<code class="parameter">array</code> equal to <strong><code>FALSE</code></strong> (see
<a href="language.types.boolean.html#language.types.boolean.casting" class="link">converting to
boolean</a>) will be removed.
</p>
</dd>
<dt>
<code class="parameter">flag</code></dt>
<dd>
<p class="para">
Flag determining what arguments are sent to <code class="parameter">callback</code>:
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara"><strong><code>ARRAY_FILTER_USE_KEY</code></strong> - pass key as the only argument
to <code class="parameter">callback</code> instead of the value</span>
</li>
<li class="listitem">
<span class="simpara"><strong><code>ARRAY_FILTER_USE_BOTH</code></strong> - pass both value and key as
arguments to <code class="parameter">callback</code> instead of the value</span>
</li>
</ul>
Default is <em>0</em> which will pass value as the only argument
to <code class="parameter">callback</code> instead.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.array-filter-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the filtered array.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.array-filter-changelog">
<h3 class="title">Changelog</h3>
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.6.0</td>
<td>
Added optional <code class="parameter">flag</code> parameter and constants
<strong><code>ARRAY_FILTER_USE_KEY</code></strong> and
<strong><code>ARRAY_FILTER_USE_BOTH</code></strong>
</td>
</tr>
</tbody>
</table>
</div>
<div class="refsect1 examples" id="refsect1-function.array-filter-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-6157">
<p><strong>Example #1 <span class="function"><strong>array_filter()</strong></span> example</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">odd</span><span style="color: #007700">(</span><span style="color: #0000BB">$var</span><span style="color: #007700">)<br />{<br /> </span><span style="color: #FF8000">// returns whether the input integer is odd<br /> </span><span style="color: #007700">return(</span><span style="color: #0000BB">$var </span><span style="color: #007700">& </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br />}<br /><br />function </span><span style="color: #0000BB">even</span><span style="color: #007700">(</span><span style="color: #0000BB">$var</span><span style="color: #007700">)<br />{<br /> </span><span style="color: #FF8000">// returns whether the input integer is even<br /> </span><span style="color: #007700">return(!(</span><span style="color: #0000BB">$var </span><span style="color: #007700">& </span><span style="color: #0000BB">1</span><span style="color: #007700">));<br />}<br /><br /></span><span style="color: #0000BB">$array1 </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"a"</span><span style="color: #007700">=></span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">"b"</span><span style="color: #007700">=></span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #DD0000">"c"</span><span style="color: #007700">=></span><span style="color: #0000BB">3</span><span style="color: #007700">, </span><span style="color: #DD0000">"d"</span><span style="color: #007700">=></span><span style="color: #0000BB">4</span><span style="color: #007700">, </span><span style="color: #DD0000">"e"</span><span style="color: #007700">=></span><span style="color: #0000BB">5</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$array2 </span><span style="color: #007700">= array(</span><span style="color: #0000BB">6</span><span style="color: #007700">, </span><span style="color: #0000BB">7</span><span style="color: #007700">, </span><span style="color: #0000BB">8</span><span style="color: #007700">, </span><span style="color: #0000BB">9</span><span style="color: #007700">, </span><span style="color: #0000BB">10</span><span style="color: #007700">, </span><span style="color: #0000BB">11</span><span style="color: #007700">, </span><span style="color: #0000BB">12</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"Odd :\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">array_filter</span><span style="color: #007700">(</span><span style="color: #0000BB">$array1</span><span style="color: #007700">, </span><span style="color: #DD0000">"odd"</span><span style="color: #007700">));<br />echo </span><span style="color: #DD0000">"Even:\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">array_filter</span><span style="color: #007700">(</span><span style="color: #0000BB">$array2</span><span style="color: #007700">, </span><span style="color: #DD0000">"even"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Odd :
Array
(
[a] => 1
[c] => 3
[e] => 5
)
Even:
Array
(
[0] => 6
[2] => 8
[4] => 10
[6] => 12
)
</pre></div>
</div>
</div>
<div class="example" id="example-6158">
<p><strong>Example #2 <span class="function"><strong>array_filter()</strong></span> without
<code class="parameter">callback</code></strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$entry </span><span style="color: #007700">= array(<br /> </span><span style="color: #0000BB">0 </span><span style="color: #007700">=> </span><span style="color: #DD0000">'foo'</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">1 </span><span style="color: #007700">=> </span><span style="color: #0000BB">false</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">2 </span><span style="color: #007700">=> -</span><span style="color: #0000BB">1</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">3 </span><span style="color: #007700">=> </span><span style="color: #0000BB">null</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">4 </span><span style="color: #007700">=> </span><span style="color: #DD0000">''<br /> </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_filter</span><span style="color: #007700">(</span><span style="color: #0000BB">$entry</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[0] => foo
[2] => -1
)
</pre></div>
</div>
</div>
<div class="example" id="example-6159">
<p><strong>Example #3 <span class="function"><strong>array_filter()</strong></span> with
<code class="parameter">flag</code></strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$arr </span><span style="color: #007700">= [</span><span style="color: #DD0000">'a' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'b' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #DD0000">'c' </span><span style="color: #007700">=> </span><span style="color: #0000BB">3</span><span style="color: #007700">, </span><span style="color: #DD0000">'d' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</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_filter</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr</span><span style="color: #007700">, function(</span><span style="color: #0000BB">$k</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">$k </span><span style="color: #007700">== </span><span style="color: #DD0000">'b'</span><span style="color: #007700">;<br />}, </span><span style="color: #0000BB">ARRAY_FILTER_USE_KEY</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">array_filter</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr</span><span style="color: #007700">, function(</span><span style="color: #0000BB">$v</span><span style="color: #007700">, </span><span style="color: #0000BB">$k</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">$k </span><span style="color: #007700">== </span><span style="color: #DD0000">'b' </span><span style="color: #007700">|| </span><span style="color: #0000BB">$v </span><span style="color: #007700">== </span><span style="color: #0000BB">4</span><span style="color: #007700">;<br />}, </span><span style="color: #0000BB">ARRAY_FILTER_USE_BOTH</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) {
["b"]=>
int(2)
}
array(2) {
["b"]=>
int(2)
["d"]=>
int(4)
}
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.array-filter-notes">
<h3 class="title">Notes</h3>
<div class="caution"><strong class="caution">Caution</strong>
<p class="para">
If the array is changed from the callback function (e.g. element
added, deleted or unset) the behavior of this function is undefined.
</p>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.array-filter-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.array-map.html" class="function" rel="rdfs-seeAlso">array_map()</a> - Applies the callback to the elements of the given arrays</span></li>
<li class="member"><span class="function"><a href="function.array-reduce.html" class="function" rel="rdfs-seeAlso">array_reduce()</a> - Iteratively reduce the array to a single value using a callback function</span></li>
<li class="member"><span class="function"><a href="function.array-walk.html" class="function" rel="rdfs-seeAlso">array_walk()</a> - Apply a user supplied function to every member of an array</span></li>
</ul>
</p>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.array-fill.html">array_fill</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.array-flip.html">array_flip</a></div>
<div class="up"><a href="ref.array.html">Array Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
