<!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>Iteratively reduce the array to a single value 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-rand.html">array_rand</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.array-replace-recursive.html">array_replace_recursive</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-reduce" class="refentry">
<div class="refnamediv">
<h1 class="refname">array_reduce</h1>
<p class="verinfo">(PHP 4 >= 4.0.5, PHP 5)</p><p class="refpurpose"><span class="refname">array_reduce</span> — <span class="dc-title">Iteratively reduce the array to a single value using a callback function</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.array-reduce-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>array_reduce</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"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$initial</code><span class="initializer"> = <strong><code>NULL</code></strong></span></span>
] )</div>
<p class="para rdfs-comment">
<span class="function"><strong>array_reduce()</strong></span> applies iteratively the
<em><code class="parameter">callback</code></em> function to the elements of the
<em><code class="parameter">array</code></em>, so as to reduce the array to
a single value.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.array-reduce-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">array</code></em></span>
<dd>
<p class="para">
The input array.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">callback</code></em></span>
<dd>
<p class="para">
The callback function.
</p>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><span class="replaceable">callback</span></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter reference">&$result</code></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$item</code></span>
)</div>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">initial</code></em></span>
<dd>
<p class="para">
If the optional <em><code class="parameter">initial</code></em> is available, it will
be used at the beginning of the process, or as a final result in case
the array is empty.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.array-reduce-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the resulting value.
</p>
<p class="para">
If the array is empty and <em><code class="parameter">initial</code></em> is not passed,
<span class="function"><strong>array_reduce()</strong></span> returns <strong><code>NULL</code></strong>.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.array-reduce-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.3.0</td>
<td>
Changed <em><code class="parameter">initial</code></em> to allow <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>, previously <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.array-reduce-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4975">
<p><strong>Example #1 <span class="function"><strong>array_reduce()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">rsum</span><span style="color: #007700">(</span><span style="color: #0000BB">$v</span><span style="color: #007700">, </span><span style="color: #0000BB">$w</span><span style="color: #007700">)<br />{<br /> </span><span style="color: #0000BB">$v </span><span style="color: #007700">+= </span><span style="color: #0000BB">$w</span><span style="color: #007700">;<br /> return </span><span style="color: #0000BB">$v</span><span style="color: #007700">;<br />}<br /><br />function </span><span style="color: #0000BB">rmul</span><span style="color: #007700">(</span><span style="color: #0000BB">$v</span><span style="color: #007700">, </span><span style="color: #0000BB">$w</span><span style="color: #007700">)<br />{<br /> </span><span style="color: #0000BB">$v </span><span style="color: #007700">*= </span><span style="color: #0000BB">$w</span><span style="color: #007700">;<br /> return </span><span style="color: #0000BB">$v</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$a </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">$x </span><span style="color: #007700">= array();<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">array_reduce</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">, </span><span style="color: #DD0000">"rsum"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= </span><span style="color: #0000BB">array_reduce</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">, </span><span style="color: #DD0000">"rmul"</span><span style="color: #007700">, </span><span style="color: #0000BB">10</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$d </span><span style="color: #007700">= </span><span style="color: #0000BB">array_reduce</span><span style="color: #007700">(</span><span style="color: #0000BB">$x</span><span style="color: #007700">, </span><span style="color: #DD0000">"rsum"</span><span style="color: #007700">, </span><span style="color: #DD0000">"No data to reduce"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>
This will result in <var class="varname"><var class="varname">$b</var></var> containing
<em>15</em>, <var class="varname"><var class="varname">$c</var></var> containing
<em>1200</em> (= 10*1*2*3*4*5), and <var class="varname"><var class="varname">$d</var></var>
containing <em>No data to reduce</em>.
</p></div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.array-reduce-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.array-filter.html" class="function" rel="rdfs-seeAlso">array_filter()</a> - Filters elements of an array using a callback function</span></li>
<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-unique.html" class="function" rel="rdfs-seeAlso">array_unique()</a> - Removes duplicate values from an array</span></li>
<li class="member"> <span class="function"><a href="function.array-count-values.html" class="function" rel="rdfs-seeAlso">array_count_values()</a> - Counts all the values 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-rand.html">array_rand</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.array-replace-recursive.html">array_replace_recursive</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>
