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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>Comparison Operators</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="language.operators.bitwise.html">Bitwise Operators</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.operators.errorcontrol.html">Error Control Operators</a></div> <div class="up"><a href="language.operators.html">Operators</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.operators.comparison" class="sect1"> <h2 class="title">Comparison Operators</h2> <p class="simpara"> Comparison operators, as their name implies, allow you to compare two values. You may also be interested in viewing <a href="types.comparisons.html" class="link">the type comparison tables</a>, as they show examples of various type related comparisons. </p> <table border="5"> <caption><b>Comparison Operators</b></caption> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Example</th> <th colspan="1">Name</th> <th colspan="1">Result</th> </tr> </thead> <tbody valign="middle" class="tbody"> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a == $b</td> <td colspan="1" rowspan="1" align="left">Equal</td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is equal to $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a === $b</td> <td colspan="1" rowspan="1" align="left">Identical</td> <td colspan="1" rowspan="1" align="left"> <b><tt>TRUE</tt></b> if $a is equal to $b, and they are of the same type. (introduced in PHP 4) </td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a != $b</td> <td colspan="1" rowspan="1" align="left">Not equal</td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is not equal to $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a <> $b</td> <td colspan="1" rowspan="1" align="left">Not equal</td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is not equal to $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a !== $b</td> <td colspan="1" rowspan="1" align="left">Not identical</td> <td colspan="1" rowspan="1" align="left"> <b><tt>TRUE</tt></b> if $a is not equal to $b, or they are not of the same type. (introduced in PHP 4) </td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a < $b</td> <td colspan="1" rowspan="1" align="left">Less than</td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is strictly less than $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a > $b</td> <td colspan="1" rowspan="1" align="left">Greater than</td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is strictly greater than $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a <= $b</td> <td colspan="1" rowspan="1" align="left">Less than or equal to </td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is less than or equal to $b.</td> </tr> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">$a >= $b</td> <td colspan="1" rowspan="1" align="left">Greater than or equal to </td> <td colspan="1" rowspan="1" align="left"><b><tt>TRUE</tt></b> if $a is greater than or equal to $b.</td> </tr> </tbody> </colgroup> </table> <p class="para"> If you compare an integer with a string, the string is <a href="language.types.string.html#language.types.string.conversion" class="link">converted to a number</a>. If you compare two numerical strings, they are compared as integers. These rules also apply to the <a href="control-structures.switch.html" class="link">switch</a> statement. <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">0 </span><span style="color: #007700">== </span><span style="color: #DD0000">"a"</span><span style="color: #007700">); </span><span style="color: #FF8000">// 0 == 0 -> true<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #DD0000">"1" </span><span style="color: #007700">== </span><span style="color: #DD0000">"01"</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1 == 1 -> true<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #DD0000">"1" </span><span style="color: #007700">== </span><span style="color: #DD0000">"1e0"</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1 == 1 -> true<br /><br /></span><span style="color: #007700">switch (</span><span style="color: #DD0000">"a"</span><span style="color: #007700">) {<br />case </span><span style="color: #0000BB">0</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"0"</span><span style="color: #007700">;<br /> break;<br />case </span><span style="color: #DD0000">"a"</span><span style="color: #007700">: </span><span style="color: #FF8000">// never reached because "a" is already matched with 0<br /> </span><span style="color: #007700">echo </span><span style="color: #DD0000">"a"</span><span style="color: #007700">;<br /> break;<br />}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> For various types, comparison is done according to the following table (in order). </p> <table border="5"> <caption><b>Comparison with Various Types</b></caption> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Type of Operand 1</th> <th colspan="1">Type of Operand 2</th> <th colspan="1">Result</th> </tr> </thead>⌨️ 快捷键说明
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