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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.8 $ -->
<!-- splitted from ./en/functions/pcntl.xml, last change in rev 1.2 -->
<refentry id="function.pcntl-signal">
<refnamediv>
<refname>pcntl_signal</refname>
<refpurpose>Installs a signal handler</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>bool</type><methodname>pcntl_signal</methodname>
<methodparam><type>int</type><parameter>signo</parameter></methodparam>
<methodparam><type>callback</type><parameter>handle</parameter></methodparam>
<methodparam choice="opt"><type>bool</type><parameter>restart_syscalls</parameter></methodparam>
</methodsynopsis>
<para>
The <function>pcntl_signal</function> function installs a new
signal handler for the signal indicated by
<parameter>signo</parameter>. The signal handler is set to
<parameter>handler</parameter> which may be the name of a user
created function, or either of the two global constants SIG_IGN
or SIG_DFL. The optional <parameter>restart_syscalls</parameter>
specifies whether system call restarting should be used when this
signal arrives and defaults to &true;.
</para>
<para>
&return.success;
</para>
<note>
<para>
The optional <parameter>restart_syscalls</parameter> parameter became
available in PHP 4.3.0.
</para>
</note>
<note>
<para>
The ability to use an object method as a callback became available in
PHP 4.3.0. 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.
</para>
</note>
<example>
<title><function>pcntl_signal</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// tick use required as of PHP 4.3.0
declare(ticks = 1);
// signal handler function
function sig_handler($signo)
{
switch ($signo) {
case SIGTERM:
// handle shutdown tasks
exit;
break;
case SIGHUP:
// handle restart tasks
break;
case SIGUSR1:
echo "Caught SIGUSR1...\n";
break;
default:
// handle all other signals
}
}
echo "Installing signal handler...\n";
// setup signal handlers
pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGHUP, "sig_handler");
pcntl_signal(SIGUSR1, "sig_handler");
// or use an object, available as of PHP 4.3.0
// pcntl_signal(SIGUSR1, array($obj, "do_something");
echo"Generating signal SIGTERM to self...\n";
// send SIGUSR1 to current process id
posix_kill(posix_getpid(), SIGUSR1);
echo "Done\n"
?>
]]>
</programlisting>
</example>
<note>
<para>
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
"<link linkend="control-structures.declare.ticks">user ticks</link>". You
must use the <link linkend="control-structures.declare">declare()</link>
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).
</para>
</note>
<para>
See also <function>pcntl_fork</function> and
<function>pcntl_waitpid</function>.
</para>
</refsect1>
</refentry>
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