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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 332508 $ -->
<refentry xml:id="function.pcntl-signal" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>pcntl_signal</refname>
<refpurpose>Installs a signal handler</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>bool</type><methodname>pcntl_signal</methodname>
<methodparam><type>int</type><parameter>signo</parameter></methodparam>
<methodparam><type>callable|int</type><parameter>handler</parameter></methodparam>
<methodparam choice="opt"><type>bool</type><parameter>restart_syscalls</parameter><initializer>true</initializer></methodparam>
</methodsynopsis>
<para>
The <function>pcntl_signal</function> function installs a new
signal handler or replaces the current signal handler for the signal indicated by <parameter>signo</parameter>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>signo</parameter></term>
<listitem>
<para>
The signal number.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>handler</parameter></term>
<listitem>
<para>
The signal handler. This may be either a <type>callable</type>, which
will be invoked to handle the signal, or either of the two global
constants <constant>SIG_IGN</constant> or <constant>SIG_DFL</constant>,
which will ignore the signal or restore the default signal handler
respectively.
</para>
<para>
If a <type>callable</type> is given, it must implement the following
signature:
</para>
<para>
<methodsynopsis>
<type>void</type><methodname><replaceable>handler</replaceable></methodname>
<methodparam><type>int</type><parameter>signo</parameter></methodparam>
</methodsynopsis>
<variablelist>
<varlistentry>
<term><parameter>signo</parameter></term>
<listitem>
<simpara>
The signal being handled.
</simpara>
</listitem>
</varlistentry>
</variablelist>
</para>
<note>
<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.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>restart_syscalls</parameter></term>
<listitem>
<para>
Specifies whether system call restarting should be used when this
signal arrives.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
&return.success;
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>4.3.0</entry>
<entry>
The <parameter>restart_syscalls</parameter> parameter was added.
</entry>
</row>
<row>
<entry>4.3.0</entry>
<entry>
The ability to use an object method as a callback became available.
</entry>
</row>
<row>
<entry>4.3.0</entry>
<entry>
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
example below).
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<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>
</para>
</refsect1>
<refsect1 role="notes"><!-- {{{ -->
&reftitle.notes;
<para>
<function>pcntl_signal</function> doesn't stack the signal handlers, but replaces them.
</para>
</refsect1><!-- }}} -->
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>pcntl_fork</function></member>
<member><function>pcntl_waitpid</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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