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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Iteratively reduce the array to a single value using a callback function</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div 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-reverse.html">array_reverse</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"> <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"><b><b>array_reduce</b></b></span> ( <span class="methodparam"><span class="type">array</span> <tt class="parameter">$input</tt></span> , <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$function</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$initial</tt></span> ] )</div> <p class="para rdfs-comment"> <b>array_reduce()</b> applies iteratively the <i><tt class="parameter">function</tt></i> function to the elements of the array <i><tt class="parameter">input</tt></i>, so as to reduce the array to a single value. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">input</tt></i></span> <dd> <p class="para"> The input array. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">function</tt></i></span> <dd> <p class="para"> The callback function. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">initial</tt></i></span> <dd> <p class="para"> If the optional <i><tt class="parameter">initial</tt></i> is available, it will be used at the beginning of the process, or as a final result in case the array is empty. </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns the resulting value. </p> <p class="para"> If the array is empty and <i><tt class="parameter">initial</tt></i> is not passed, <b>array_reduce()</b> returns <b><tt>NULL</tt></b>. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 <b>array_reduce()</b> example</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">rsum</span><span style="color: #007700">(</span><span style="color: #0000BB">$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">$x</span><span style="color: #007700">, </span><span style="color: #DD0000">"rsum"</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> <div class="example-contents"><p> This will result in <var class="varname">$b</var> containing <i>15</i>, <var class="varname">$c</var> containing <i>1200</i> (= 10*1*2*3*4*5), and <var class="varname">$d</var> containing <i>1</i>. </p></div> </div> </p> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.array-filter.html" class="function" rel="rdfs-seeAlso">array_filter()</a></li> <li class="member"><a href="function.array-map.html" class="function" rel="rdfs-seeAlso">array_map()</a></li> <li class="member"><a href="function.array-unique.html" class="function" rel="rdfs-seeAlso">array_unique()</a></li> <li class="member"><a href="function.array-count-values.html" class="function" rel="rdfs-seeAlso">array_count_values()</a></li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: 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