language.types.resource.html
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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>Resources</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.types.object.html">Objects</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.types.null.html">NULL</a></div> <div class="up"><a href="language.types.html">Types</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.types.resource" class="sect1"> <h2 class="title">Resources</h2> <p class="para"> A <a href="language.types.resource.html" class="type resource">resource</a> 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 <a href="language.types.resource.html" class="type resource">resource</a> types. </p> <blockquote><p><b class="note">Note</b>: <span class="simpara"> The <a href="language.types.resource.html" class="type resource">resource</a> type was introduced in PHP 4 </span> </p></blockquote> <p class="para"> See also the <a href="function.get-resource-type.html" class="function">get_resource_type()</a> function. </p> <div id="language.types.resource.casting" class="sect2"> <h3 class="title">Converting to resource</h3> <p class="para"> As <a href="language.types.resource.html" class="type resource">resource</a> variables hold special handlers to opened files, database connections, image canvas areas and the like, converting to a <a href="language.types.resource.html" class="type resource">resource</a> makes no sense. </p> </div> <div id="language.types.resource.self-destruct" class="sect2"> <h3 class="title">Freeing resources</h3> <p class="para"> Thanks to the reference-counting system introduced with PHP 4's Zend Engine, a <a href="language.types.resource.html" class="type resource">resource</a> 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><p><b class="note">Note</b>: <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> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.types.object.html">Objects</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.types.null.html">NULL</a></div> <div class="up"><a href="language.types.html">Types</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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