language.namespaces.using.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>Using namespaces</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.namespaces.definition.html">Namespace definition</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.namespaces.global.html">Global space</a></div> <div class="up"><a href="language.namespaces.html">Namespaces</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.namespaces.using" class="sect1"> <h2 class="title">Using namespaces</h2> <p class="para"> Every class and function in a namespace can be referred to by the full name - e.g. <b class="classname">MyProject::DB::Connection</b> or <b class="classname">MyProject::DB::connect</b> - at any time. <div class="example"> <p><b>Example #1 Using namespaced name</b></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /> </span><span style="color: #007700">require </span><span style="color: #DD0000">'MyProject/Db/Connection.php'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$x </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyProject</span><span style="color: #007700">::</span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">Connection</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">MyProject</span><span style="color: #007700">::</span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">connect</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> Namespaces can be imported into current context (global or namespace) using the <i>use</i> operator. The syntax for the operator is: <div class="informalexample"> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* ... */<br /></span><span style="color: #007700">use </span><span style="color: #0000BB">Some</span><span style="color: #007700">::</span><span style="color: #0000BB">Name </span><span style="color: #007700">as </span><span style="color: #0000BB">Othername</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// The simplified form of use:<br /></span><span style="color: #007700">use </span><span style="color: #0000BB">Foo</span><span style="color: #007700">::</span><span style="color: #0000BB">Bar</span><span style="color: #007700">;<br /></span><span style="color: #FF8000">// which is the same as :<br /></span><span style="color: #007700">use </span><span style="color: #0000BB">Foo</span><span style="color: #007700">::</span><span style="color: #0000BB">Bar </span><span style="color: #007700">as </span><span style="color: #0000BB">Bar</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> The imported name works as follows: every time that the compiler encounters the local name <i>Othername</i> (as stand-alone name or as prefix to the longer name separated by <i>::</i>) the imported name <i>Some::Name</i> is substituted instead. </p> <p class="para"> <i>use</i> can be used only in global scope, not inside function or class. Imported names have effect from the point of import to the end of the current file. It is recommended to put imports at the beginning of the file to avoid confusion. </p> <p class="para"> <div class="example"> <p><b>Example #2 Importing and accessing namespace</b></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /> </span><span style="color: #007700">require </span><span style="color: #DD0000">'MyProject/Db/Connection.php'</span><span style="color: #007700">;<br /> use </span><span style="color: #0000BB">MyProject</span><span style="color: #007700">::</span><span style="color: #0000BB">DB</span><span style="color: #007700">;<br /> use </span><span style="color: #0000BB">MyProject</span><span style="color: #007700">::</span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">Connection </span><span style="color: #007700">as </span><span style="color: #0000BB">DbConnection</span><span style="color: #007700">;<br /> <br /> </span><span style="color: #0000BB">$x </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyProject</span><span style="color: #007700">::</span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">Connection</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">$y </span><span style="color: #007700">= new </span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">connection</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">$z </span><span style="color: #007700">= new </span><span style="color: #0000BB">DbConnection</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">DB</span><span style="color: #007700">::</span><span style="color: #0000BB">connect</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> <blockquote><p><b class="note">Note</b>: <span class="simpara"> The import operation is compile-time only, all local names are converted to their full equivalents by the compiler. Note that it won't translate names in strings, so callbacks can't rely on import rules. </span> </p></blockquote> </p> </div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.namespaces.definition.html">Namespace definition</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.namespaces.global.html">Global space</a></div> <div class="up"><a href="language.namespaces.html">Namespaces</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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