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<title>Type Operators</title>
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</div><hr /><div id="language.operators.type" class="sect1">
<h2 class="title">Type Operators</h2>
<p class="para">
<em>instanceof</em> 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" id="example-128">
<p><strong>Example #1 Using <em>instanceof</em> with classes</strong></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">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">NotMyClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(false)
</pre></div>
</div>
</div>
</p>
<p class="para">
<em>instanceof</em> can also be used to determine whether a variable
is an instantiated object of a class that inherits from a parent class:
<div class="example" id="example-129">
<p><strong>Example #2 Using <em>instanceof</em> with inherited classes</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">extends </span><span style="color: #0000BB">ParentClass<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$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 screen">
<div class="cdata"><pre>
bool(true)
bool(true)
</pre></div>
</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 <em>not</em>
operator</a> can be used.
<div class="example" id="example-130">
<p><strong>Example #3 Using <em>instanceof</em> to check if object is <em class="emphasis">not</em> an
instanceof a class</strong></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 screen">
<div class="cdata"><pre>
bool(true)
</pre></div>
</div>
</div>
</p>
<p class="para">
Lastly, <em>instanceof</em> 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" id="example-131">
<p><strong>Example #4 Using <em>instanceof</em> for class</strong></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">$a </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">MyInterface</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(true)
</pre></div>
</div>
</div>
</p>
<p class="para">
Although <em>instanceof</em> is usually used with a literal classname,
it can also be used with another object or a string variable:
<div class="example" id="example-132">
<p><strong>Example #5 Using <em>instanceof</em> with other variables</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">interface </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br />class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">implements </span><span style="color: #0000BB">MyInterface<br /></span><span style="color: #007700">{<br />}<br /><br /></span><span style="color: #0000BB">$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">// $d is a string 'NotMyClass'<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(true)
bool(false)
</pre></div>
</div>
</div>
</p>
<p class="para">
instanceof does not throw any error if the variable being tested is not
an object, it simply returns <strong><code>FALSE</code></strong>. Constants, however, are not allowed.
<div class="example" id="example-133">
<p><strong>Example #6 Using <em>instanceof</em> to test other variables</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$a </span><span style="color: #007700">= </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">NULL</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= </span><span style="color: #0000BB">imagecreate</span><span style="color: #007700">(</span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">5</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">); </span><span style="color: #FF8000">// $a is an integer<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$b </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">); </span><span style="color: #FF8000">// $b is NULL<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$c </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">); </span><span style="color: #FF8000">// $c is a resource<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">FALSE </span><span style="color: #007700">instanceof </span><span style="color: #0000BB">stdClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
bool(false)
bool(false)
bool(false)
PHP Fatal error: instanceof expects an object instance, constant given
</pre></div>
</div>
</div>
</p>
<p class="para">
There are a few pitfalls to be aware of. Before PHP version 5.1.0,
<em>instanceof</em> would call <span class="function"><a href="function.autoload.html" class="function">__autoload()</a></span>
if the class name did not exist. In addition, if the class was not loaded,
a fatal error would occur. This can be worked around by using a dynamic
class reference, or a string variable containing the class name:
<div class="example" id="example-134">
<p><strong>Example #7 Avoiding classname lookups and fatal errors with <em>instanceof</em> in PHP 5.0</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$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 screen">
<div class="cdata"><pre>
bool(false)
</pre></div>
</div>
</div>
</p>
<p class="simpara">
The <em>instanceof</em> operator was introduced in PHP 5.
Before this time <span class="function"><a href="function.is-a.html" class="function">is_a()</a></span> was used but
<span class="function"><a href="function.is-a.html" class="function">is_a()</a></span> has since been deprecated in favor of
<em>instanceof</em>. Note that as of PHP 5.3.0,
<span class="function"><a href="function.is-a.html" class="function">is_a()</a></span> is no longer deprecated.
</p>
<p class="para">
See also <span class="function"><a href="function.get-class.html" class="function">get_class()</a></span> and
<span class="function"><a href="function.is-a.html" class="function">is_a()</a></span>.
</p>
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