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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>Type 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.html">Operators</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.control-structures.html">Control Structures</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.type" class="sect1"> <h2 class="title">Type Operators</h2> <p class="para"> <i>instanceof</i> is used to determine whether a PHP variable is an instantiated object of a certain <a href="language.oop5.basic.html#language.oop5.basic.class" class="link">class</a>: <div class="example"> <p><b>Example #1 Using instanceof with classes</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">class </span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">NotMyClass<br /></span><span style="color: #007700">{<br />}<br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">NotMyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents"><pre><div class="cdata"><pre>bool(true)bool(false)</pre></div> </pre></div> </div> </p> <p class="para"> <i>instanceof</i> can also be used to determine whether a variable is an instantiated object of a class that inherits from a parent class: <div class="example"> <p><b>Example #2 Using instanceof with inherited classes</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">extends </span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">ParentClass</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"><pre><div class="cdata"><pre>bool(true)bool(true)</pre></div> </pre></div> </div> </p> <p class="para"> To check if an object is <em class="emphasis">not</em> an instanceof a class, the <a href="language.operators.logical.html" class="link">logical <i>not</i> operator</a> can be used. <div class="example"> <p><b>Example #3 Using instanceof to check if object is <em class="emphasis">not</em> an instanceof a class</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">class </span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(!(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">stdClass</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"><pre><div class="cdata"><pre>bool(true)</pre></div> </pre></div> </div> </p> <p class="para"> Lastly, <i>instanceof</i> can also be used to determine whether a variable is an instantiated object of a class that implements an <a href="language.oop5.interfaces.html" class="link">interface</a>: <div class="example"> <p><b>Example #4 Using instanceof for class</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">interface </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">implements </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">MyInterface</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents"><pre><div class="cdata"><pre>bool(true)bool(true)</pre></div> </pre></div> </div> </p> <p class="para"> Although <i>instanceof</i> is usually used with a literal classname, it can also be used with another object or a string variable: <div class="example"> <p><b>Example #5 Using instanceof with other variables</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #007700">interface </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">implements </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= </span><span style="color: #DD0000">'MyClass'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$d </span><span style="color: #007700">= </span><span style="color: #DD0000">'NotMyClass'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">$b</span><span style="color: #007700">); </span><span style="color: #FF8000">// $b is an object of class MyClass<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">$c</span><span style="color: #007700">); </span><span style="color: #FF8000">// $c is a string 'MyClass'<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">$d</span><span style="color: #007700">); </span><span style="color: #FF8000">// $d is a string 'NotMyClass'<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents"><pre><div class="cdata"><pre>bool(true)bool(true)bool(false)</pre></div> </pre></div> </div> </p> <p class="para"> There are a few pitfalls to be aware of. Before PHP version 5.1.0, <i>instanceof</i> would call <a href="language.oop5.autoload.html" class="link">__autoload()</a> if the class name did not exist. In addition, if the class was not loaded, a fatal error would occur. This can be worked around by using a <i>dynamic class reference</i>, or a string variable containing the class name: <div class="example"> <p><b>Example #6 Avoiding classname lookups and fatal errors with instanceof in PHP 5.0</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br />$d </span><span style="color: #007700">= </span><span style="color: #DD0000">'NotMyClass'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">$d</span><span style="color: #007700">); </span><span style="color: #FF8000">// no fatal error here<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"><pre><div class="cdata"><pre>bool(false)</pre></div> </pre></div> </div> </p> <p class="simpara"> The <i>instanceof</i> operator was introduced in PHP 5. Before this time <a href="function.is-a.html" class="function">is_a()</a> was used but <a href="function.is-a.html" class="function">is_a()</a> has since been deprecated in favor of <i>instanceof</i>. </p> <p class="para"> See also <a href="function.get-class.html" class="function">get_class()</a> and <a href="function.is-a.html" class="function">is_a()</a>. </p> </div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.operators.html">Operators</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.control-structures.html">Control Structures</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></body></html>⌨️ 快捷键说明
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