Source of: /manual/en/function.pcntl-signal.php
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<div id="function.pcntl-signal" class="refentry">
<div class="refnamediv">
<h1 class="refname">pcntl_signal</h1>
<p class="verinfo">(PHP 4 >= 4.1.0, PHP 5)</p><p class="refpurpose"><span class="refname">pcntl_signal</span> — <span class="dc-title">Installs a signal handler</span></p>
</div>
<a name="function.pcntl-signal.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><b>pcntl_signal</b></span>
( <span class="methodparam"><span class="type">int</span> <tt class="parameter">$signo</tt></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.php#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$handler</tt></span>
[, <span class="methodparam"><span class="type">bool</span> <tt class="parameter">$restart_syscalls</tt><span class="initializer"> = true</span></span>
] )</div>
<p class="para rdfs-comment">
The <b>pcntl_signal()</b> function installs a new
signal handler for the signal indicated by <i><tt class="parameter">signo</tt></i>
.
</p>
</div>
<a name="function.pcntl-signal.parameters"></a><div class="refsect1 parameters">
<h3 class="title">Parameters</h3>
<p class="para">
</p><dl>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">signo</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The signal number.
</p>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">handler</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The signal handler which may be the name of a user created function,
or method, or either of the two global constants
<b><tt class="constant">SIG_IGN</tt></b> or <b><tt class="constant">SIG_DFL</tt></b>.
</p>
<blockquote><p><b class="note">Note</b>:
Note that when you set a handler to an object method, that object's
reference count is increased which makes it persist until you either
change the handler to something else, or your script ends.
<br />
</p></blockquote>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">restart_syscalls</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
Specifies whether system call restarting should be used when this
signal arrives and defaults to <b><tt class="constant">TRUE</tt></b>.
</p>
</dd>
</dl>
<p>
</p>
</div>
<a name="function.pcntl-signal.returnvalues"></a><div class="refsect1 returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <b><tt class="constant">TRUE</tt></b> on success or <b><tt class="constant">FALSE</tt></b> on failure.
</p>
</div>
<a name="function.pcntl-signal.changelog"></a><div class="refsect1 changelog">
<h3 class="title">Changelog</h3>
<p class="para">
</p><table class="doctable informaltable">
<thead valign="middle">
<tr valign="middle">
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody valign="middle" class="tbody">
<tr valign="middle">
<td align="left">4.3.0</td>
<td align="left">
The <i><tt class="parameter">restart_syscalls</tt></i>
parameter was added.
</td>
</tr>
<tr valign="middle">
<td align="left">4.3.0</td>
<td align="left">
The ability to use an object method as a callback became available.
</td>
</tr>
<tr valign="middle">
<td align="left">4.3.0</td>
<td align="left">
As of PHP 4.3.0 PCNTL uses ticks as the signal handle callback
mechanism, which is much faster than the previous mechanism. This
change follows the same semantics as using
"<a href="control-structures.declare.php#control-structures.declare.ticks" class="link">user ticks</a>".
You must use the <a href="control-structures.declare.php" class="link">declare()</a> statement to
specify the locations in your program where callbacks are allowed to
occur for the signal handler to function properly (as used in the
above example).
</td>
</tr>
</tbody>
</table>
<p>
</p>
</div>
<a name="function.pcntl-signal.examples"></a><div class="refsect1 examples">
<h3 class="title">Examples</h3>
<p class="para">
</p><div class="example">
<p><b>Example #1 <b>pcntl_signal()</b> example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// tick use required as of PHP 4.3.0<br /></span><span style="color: #007700">declare(</span><span style="color: #0000BB">ticks </span><span style="color: #007700">= </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// signal handler function<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">sig_handler</span><span style="color: #007700">(</span><span style="color: #0000BB">$signo</span><span style="color: #007700">)<br />{<br /><br /> switch (</span><span style="color: #0000BB">$signo</span><span style="color: #007700">) {<br /> case </span><span style="color: #0000BB">SIGTERM</span><span style="color: #007700">:<br /> </span><span style="color: #FF8000">// handle shutdown tasks<br /> </span><span style="color: #007700">exit;<br /> break;<br /> case </span><span style="color: #0000BB">SIGHUP</span><span style="color: #007700">:<br /> </span><span style="color: #FF8000">// handle restart tasks<br /> </span><span style="color: #007700">break;<br /> case </span><span style="color: #0000BB">SIGUSR1</span><span style="color: #007700">:<br /> echo </span><span style="color: #DD0000">"Caught SIGUSR1...\n"</span><span style="color: #007700">;<br /> break;<br /> default:<br /> </span><span style="color: #FF8000">// handle all other signals<br /> </span><span style="color: #007700">}<br /><br />}<br /><br />echo </span><span style="color: #DD0000">"Installing signal handler...\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// setup signal handlers<br /></span><span style="color: #0000BB">pcntl_signal</span><span style="color: #007700">(</span><span style="color: #0000BB">SIGTERM</span><span style="color: #007700">, </span><span style="color: #DD0000">"sig_handler"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">pcntl_signal</span><span style="color: #007700">(</span><span style="color: #0000BB">SIGHUP</span><span style="color: #007700">, </span><span style="color: #DD0000">"sig_handler"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">pcntl_signal</span><span style="color: #007700">(</span><span style="color: #0000BB">SIGUSR1</span><span style="color: #007700">, </span><span style="color: #DD0000">"sig_handler"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// or use an object, available as of PHP 4.3.0<br />// pcntl_signal(SIGUSR1, array($obj, "do_something");<br /><br /></span><span style="color: #007700">echo</span><span style="color: #DD0000">"Generating signal SIGTERM to self...\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// send SIGUSR1 to current process id<br /></span><span style="color: #0000BB">posix_kill</span><span style="color: #007700">(</span><span style="color: #0000BB">posix_getpid</span><span style="color: #007700">(), </span><span style="color: #0000BB">SIGUSR1</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"Done\n"<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div><p>
</p>
</div>
<a name="function.pcntl-signal.seealso"></a><div class="refsect1 seealso">
<h3 class="title">See Also</h3>
<p class="para">
</p><ul class="simplelist">
<li class="member"><a href="function.pcntl-fork.php" class="function" rel="rdfs-seeAlso">pcntl_fork()</a> - Forks the currently running process</li>
<li class="member"><a href="function.pcntl-waitpid.php" class="function" rel="rdfs-seeAlso">pcntl_waitpid()</a> - Waits on or returns the status of a forked child</li>
</ul><p>
</p>
</div>
</div><?php manual_footer(); ?>
