<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Get a semaphore id</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.sem-acquire.html">sem_acquire</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.sem-release.html">sem_release</a></div> <div class="up"><a href="ref.sem.html">Semaphore Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="function.sem-get" class="refentry"> <div class="refnamediv"> <h1 class="refname">sem_get</h1> <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">sem_get</span> — <span class="dc-title">Get a semaphore id</span></p> </div> <div class="refsect1 description" id="refsect1-function.sem-get-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">resource</span> <span class="methodname"><strong>sem_get</strong></span> ( <span class="methodparam"><span class="type">int</span> <code class="parameter">$key</code></span> [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$max_acquire</code><span class="initializer"> = 1</span></span> [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$perm</code><span class="initializer"> = 0666</span></span> [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$auto_release</code><span class="initializer"> = 1</span></span> ]]] )</div> <p class="para rdfs-comment"> <span class="function"><strong>sem_get()</strong></span> returns an id that can be used to access the System V semaphore with the given <em><code class="parameter">key</code></em>. </p> <p class="para"> A second call to <span class="function"><strong>sem_get()</strong></span> for the same key will return a different semaphore identifier, but both identifiers access the same underlying semaphore. </p> </div> <div class="refsect1 parameters" id="refsect1-function.sem-get-parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><em><code class="parameter">key</code></em></span> <dd> <p class="para"> </p> </dd> </dt> <dt> <span class="term"><em><code class="parameter">max_acquire</code></em></span> <dd> <p class="para"> The number of processes that can acquire the semaphore simultaneously is set to <em><code class="parameter">max_acquire</code></em>. </p> </dd> </dt> <dt> <span class="term"><em><code class="parameter">perm</code></em></span> <dd> <p class="para"> The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore. </p> </dd> </dt> <dt> <span class="term"><em><code class="parameter">auto_release</code></em></span> <dd> <p class="para"> Specifies if the semaphore should be automatically released on request shutdown. </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues" id="refsect1-function.sem-get-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns a positive semaphore identifier on success, or <strong><code>FALSE</code></strong> on error. </p> </div> <div class="refsect1 changelog" id="refsect1-function.sem-get-changelog"> <h3 class="title">Changelog</h3> <p class="para"> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>4.3.0</td> <td> The <em><code class="parameter">auto_release</code></em> parameter was added. </td> </tr> </tbody> </table> </p> </div> <div class="refsect1 notes" id="refsect1-function.sem-get-notes"> <h3 class="title">Notes</h3> <div class="warning"><strong class="warning">Warning</strong> <p class="simpara"> When using <span class="function"><strong>sem_get()</strong></span> to access a semaphore created outside PHP, note that the semaphore must have been created as a set of 3 semaphores (for example, by specifying 3 as the <em>nsems</em> parameter when calling the C <em>semget()</em> function), otherwise PHP will be unable to access the semaphore. </p> </div> </div> <div class="refsect1 seealso" id="refsect1-function.sem-get-seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"> <span class="function"><a href="function.sem-acquire.html" class="function" rel="rdfs-seeAlso">sem_acquire()</a> - Acquire a semaphore</span></li> <li class="member"> <span class="function"><a href="function.sem-release.html" class="function" rel="rdfs-seeAlso">sem_release()</a> - Release a semaphore</span></li> <li class="member"> <span class="function"><a href="function.ftok.html" class="function" rel="rdfs-seeAlso">ftok()</a> - Convert a pathname and a project identifier to a System V IPC key</span></li> </ul> </p> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.sem-acquire.html">sem_acquire</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.sem-release.html">sem_release</a></div> <div class="up"><a href="ref.sem.html">Semaphore Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>