php-doc-en/reference/pcntl/functions/pcntl-signal.xml

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<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>callback</type><parameter>handler</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>.   
  </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 which may be the name of a user created function,
       or method, or either of the two global constants 
       <constant>SIG_IGN</constant> or <constant>SIG_DFL</constant>. 
      </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 and defaults to &true;.
      </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
        above example).
       </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="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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