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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>Sort an array by values using a user-defined comparison 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="ref.array.html">Array Functions</a></div> <div class="next" style="text-align: right; float: right;"><a href="book.classobj.html">Classes/Objects</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.usort" class="refentry"> <div class="refnamediv"> <h1 class="refname">usort</h1> <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">usort</span> — <span class="dc-title">Sort an array by values using a user-defined comparison function</span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><b><b>usort</b></b></span> ( <span class="methodparam"><span class="type">array</span> <tt class="parameter reference">&$array</tt></span> , <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$cmp_function</tt></span> )</div> <p class="para rdfs-comment"> This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function. </p> <blockquote><p><b class="note">Note</b>: If two members compare as equal, their order in the sorted array is undefined. <br /> </p></blockquote> <blockquote><p><b class="note">Note</b>: <span class="simpara">This functionassigns new keys to the elements in <i><tt class="parameter">array</tt></i>.It will remove any existing keys that may have been assigned, ratherthan just reordering the keys.</span></p></blockquote> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">array</tt></i></span> <dd> <p class="para"> The input array. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">cmp_function</tt></i></span> <dd> <p class="para"> The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns <b><tt>TRUE</tt></b> on success or <b><tt>FALSE</tt></b> on failure. </p> </div> <div class="refsect1 changelog"> <h3 class="title">ChangeLog</h3> <p class="para"> <table class="informaltable"> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Version</th> <th colspan="1">Description</th> </tr> </thead> <tbody valign="middle" class="tbody"> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">4.1.0</td> <td colspan="1" rowspan="1" align="left"> A new sort algorithm was introduced. The <i><tt class="parameter">cmp_function</tt></i> doesn't keep the original order for elements comparing as equal. </td> </tr>⌨️ 快捷键说明
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