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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 1.4 $ -->
<sect1 xml:id="language.types.resource">
<title>Resources</title>
<para>
A <type>resource</type> is a special variable, holding a reference to an
external resource. Resources are created and used by special functions. See
the <link linkend="resource">appendix</link> for a listing of all these
functions and the corresponding <type>resource</type> types.
</para>
<note>
<simpara>
The <type>resource</type> type was introduced in PHP 4
</simpara>
</note>
<para>
See also the <function>get_resource_type</function> function.
</para>
<sect2 xml:id="language.types.resource.casting">
<title>Converting to resource</title>
<para>
As <type>resource</type> variables hold special handlers to opened files,
database connections, image canvas areas and the like, converting to a
<type>resource</type> makes no sense.
</para>
</sect2>
<sect2 xml:id="language.types.resource.self-destruct">
<title>Freeing resources</title>
<para>
Thanks to the reference-counting system introduced with PHP 4's Zend Engine,
a <type>resource</type> 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.
</para>
<note>
<simpara>
Persistent database links are an exception to this rule. They are
<emphasis>not</emphasis> destroyed by the garbage collector. See the
<link linkend="features.persistent-connections">persistent
connections</link> section for more information.
</simpara>
</note>
</sect2>
</sect1>
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