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<h2 class="title">Resources</h2>
<p class="para">
A <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> is a special variable, holding a reference to an
external resource. Resources are created and used by special functions. See
the <a href="resource.html" class="link">appendix</a> for a listing of all these
functions and the corresponding <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> types.
</p>
<p class="para">
See also the <span class="function"><a href="function.get-resource-type.html" class="function">get_resource_type()</a></span> function.
</p>
<div class="sect2" id="language.types.resource.casting">
<h3 class="title">Converting to resource</h3>
<p class="para">
As <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> variables hold special handlers to opened files,
database connections, image canvas areas and the like, converting to a
<span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> makes no sense.
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<div class="sect2" id="language.types.resource.self-destruct">
<h3 class="title">Freeing resources</h3>
<p class="para">
Thanks to the reference-counting system introduced with PHP 4's Zend Engine,
a <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> with no more references to it is detected
automatically, and it is freed by the garbage collector. For this reason, it
is rarely necessary to free the memory manually.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
Persistent database links are an exception to this rule. They are
<em class="emphasis">not</em> destroyed by the garbage collector. See the
<a href="features.persistent-connections.html" class="link">persistent
connections</a> section for more information.
</span>
</p></blockquote>
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