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<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>
<div class="refsect1 description" id="refsect1-function.pcntl-signal-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>pcntl_signal</strong></span>
( <span class="methodparam"><span class="type">int</span> <code class="parameter">$signo</code></span>
, <span class="methodparam"><span class="type"><span class="type callable|int">callable|int</span></span> <code class="parameter">$handler</code></span>
[, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$restart_syscalls</code><span class="initializer"> = true</span></span>
] )</div>
<p class="para rdfs-comment">
The <span class="function"><strong>pcntl_signal()</strong></span> function installs a new
signal handler or replaces the current signal handler for the signal indicated by <em><code class="parameter">signo</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.pcntl-signal-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">signo</code></em></span>
<dd>
<p class="para">
The signal number.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">handler</code></em></span>
<dd>
<p class="para">
The signal handler. This may be either a <span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span>, which
will be invoked to handle the signal, or either of the two global
constants <strong><code>SIG_IGN</code></strong> or <strong><code>SIG_DFL</code></strong>,
which will ignore the signal or restore the default signal handler
respectively.
</p>
<p class="para">
If a <span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> is given, it must implement the following
signature:
</p>
<p class="para">
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span> <span class="methodname"><span class="replaceable">handler</span></span>
( <span class="methodparam"><span class="type">int</span> <code class="parameter">$signo</code></span>
)</div>
<dl>
<dt>
<span class="term"><em><code class="parameter">signo</code></em></span>
<dd>
<span class="simpara">
The signal being handled.
</span>
</dd>
</dt>
</dl>
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
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.
</p>
</p></blockquote>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">restart_syscalls</code></em></span>
<dd>
<p class="para">
Specifies whether system call restarting should be used when this
signal arrives.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.pcntl-signal-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <strong><code>TRUE</code></strong> on success or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.pcntl-signal-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">restart_syscalls</code></em> parameter was added.
</td>
</tr>
<tr>
<td>4.3.0</td>
<td>
The ability to use an object method as a callback became available.
</td>
</tr>
<tr>
<td>4.3.0</td>
<td>
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.html#control-structures.declare.ticks" class="link">user ticks</a>".
You must use the <a href="control-structures.declare.html" 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>
</div>
<div class="refsect1 examples" id="refsect1-function.pcntl-signal-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3645">
<p><strong>Example #1 <span class="function"><strong>pcntl_signal()</strong></span> example</strong></p>
<div class="example-contents">
<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"</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.pcntl-signal-notes">
<h3 class="title">Notes</h3>
<p class="para">
<span class="function"><strong>pcntl_signal()</strong></span> doesn't stack the signal handlers, but replaces them.
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.pcntl-signal-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.pcntl-fork.html" class="function" rel="rdfs-seeAlso">pcntl_fork()</a> - Forks the currently running process</span></li>
<li class="member"> <span class="function"><a href="function.pcntl-waitpid.html" class="function" rel="rdfs-seeAlso">pcntl_waitpid()</a> - Waits on or returns the status of a forked child</span></li>
</ul>
</p>
</div>
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