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Source of: /manual/en/language.operators.type.php

<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.operators.inc";
$setup = array (
  'home' =>
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    0 => 'index.php',
    1 => 'PHP Manual',
  ),
  'head' =>
  array (
    0 => 'UTF-8',
    1 => 'en',
  ),
  'this' =>
  array (
    0 => 'language.operators.type.php',
    1 => 'Type Operators',
  ),
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  array (
    0 => 'language.operators.php',
    1 => 'Operators',
  ),
  'prev' =>
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    0 => 'language.operators.array.php',
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  ),
  'next' =>
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    0 => 'language.control-structures.php',
    1 => 'Control Structures',
  ),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);

manual_header();
?>
<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.php#language.oop5.basic.class" class="link">class</a>:
    </p><div class="example">
     <p><b>Example #1 Using instanceof with classes</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br />}<br /><br />class&nbsp;</span><span style="color: #0000BB">NotMyClass<br /></span><span style="color: #007700">{<br />}<br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</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&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">NotMyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

     <div class="example-contents para"><p>The above example will output:</p></div>
     <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(false)
</pre></div>
     </div>
    </div><p>
   </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:
    </p><div class="example">
     <p><b>Example #2 Using <i>instanceof</i> with inherited classes</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br />class&nbsp;</span><span style="color: #0000BB">MyClass&nbsp;</span><span style="color: #007700">extends&nbsp;</span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</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&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">ParentClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

     <div class="example-contents para"><p>The above example will output:</p></div>
     <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(true)
</pre></div>
     </div>
    </div><p>
   </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.php" class="link">logical <i>not</i>
    operator</a> can be used.
    </p><div class="example">
     <p><b>Example #3 Using <i>instanceof</i> to check if object is <em class="emphasis">not</em> an
      instanceof a class</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(!(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">stdClass</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
</pre></div>
     </div>
    </div><p>
   </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.php" class="link">interface</a>:
    </p><div class="example">
     <p><b>Example #4 Using <i>instanceof</i> for class</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">interface&nbsp;</span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br />class&nbsp;</span><span style="color: #0000BB">MyClass&nbsp;</span><span style="color: #007700">implements&nbsp;</span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</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&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">MyInterface</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

     <div class="example-contents para"><p>The above example will output:</p></div>
     <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(true)
</pre></div>
     </div>
    </div><p>
   </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:
    </p><div class="example">
     <p><b>Example #5 Using <i>instanceof</i> with other variables</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">interface&nbsp;</span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br />class&nbsp;</span><span style="color: #0000BB">MyClass&nbsp;</span><span style="color: #007700">implements&nbsp;</span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$c&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'MyClass'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$d&nbsp;</span><span style="color: #007700">=&nbsp;</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">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">$b</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;$b&nbsp;is&nbsp;an&nbsp;object&nbsp;of&nbsp;class&nbsp;MyClass<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">$c</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;$c&nbsp;is&nbsp;a&nbsp;string&nbsp;'MyClass'<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">$d</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;$d&nbsp;is&nbsp;a&nbsp;string&nbsp;'NotMyClass'<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(true)
bool(false)
</pre></div>
     </div>
    </div><p>
   </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.php" 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 dynamic
    class reference, or a string variable containing the class name:
    </p><div class="example">
     <p><b>Example #6 Avoiding classname lookups and fatal errors with <i>instanceof</i> in PHP 5.0</b></p>
     <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$d&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'NotMyClass'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">instanceof&nbsp;</span><span style="color: #0000BB">$d</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;no&nbsp;fatal&nbsp;error&nbsp;here<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
bool(false)
</pre></div>
     </div>
    </div><p>
   </p>
   <p class="simpara">
    The <i>instanceof</i> operator was introduced in PHP 5.
    Before this time <a href="function.is-a.php" class="function">is_a()</a> was used but
    <a href="function.is-a.php" class="function">is_a()</a> has since been deprecated in favor of
    <i>instanceof</i>. Note that as of PHP 5.3.0,
    <a href="function.is-a.php" class="function">is_a()</a> is no longer deprecated.
   </p>
   <p class="para">
    See also <a href="function.get-class.php" class="function">get_class()</a> and
    <a href="function.is-a.php" class="function">is_a()</a>.
   </p>
  </div><?php manual_footer(); ?>
 
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