php-doc-en/reference/session/functions/session-set-save-handler.xml

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<!-- $Revision: 1.16 $ -->
<refentry id="function.session-set-save-handler">
 <refnamediv>
  <refname>session_set_save_handler</refname>
  <refpurpose>Sets user-level session storage functions</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>session_set_save_handler</methodname>
   <methodparam><type>callback</type><parameter>open</parameter></methodparam>
   <methodparam><type>callback</type><parameter>close</parameter></methodparam>
   <methodparam><type>callback</type><parameter>read</parameter></methodparam>
   <methodparam><type>callback</type><parameter>write</parameter></methodparam>
   <methodparam><type>callback</type><parameter>destroy</parameter></methodparam>
   <methodparam><type>callback</type><parameter>gc</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>session_set_save_handler</function> sets the user-level
   session storage functions which are used for storing and
   retrieving data associated with a session.  This is most useful
   when a storage method other than those supplied by PHP sessions
   is preferred.  i.e. Storing the session data in a local database.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>open</parameter></term>
     <listitem>
      <para>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>close</parameter></term>
     <listitem>
      <para>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>read</parameter></term>
     <listitem>
      <para>
       Read function must return string value always to make save handler
       work as expected. Return empty string if there is no data to read.
       Return values from other handlers are converted to boolean expression.
       &true; for success, &false; for failure.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>write</parameter></term>
     <listitem>
      <para>
       <note>
        <para>
         The "write" handler is not executed until after the output stream is
         closed.  Thus, output from debugging statements in the "write"
         handler will never be seen in the browser.  If debugging output is
         necessary, it is suggested that the debug output be written to a
         file instead.
        </para>
       </note>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>destroy</parameter></term>
     <listitem>
      <para>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>gc</parameter></term>
     <listitem>
      <para>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>session_set_save_handler</function> example</title>
    <para>
     The following example provides file based session storage similar to the
     PHP sessions default save handler <parameter>files</parameter>.  This
     example could easily be extended to cover database storage using your
     favorite PHP supported database engine.
    </para>
    <programlisting role="php">
<![CDATA[
<?php
function open($save_path, $session_name)
{
  global $sess_save_path;

  $sess_save_path = $save_path;
  return(true);
}

function close()
{
  return(true);
}

function read($id)
{
  global $sess_save_path;

  $sess_file = "$sess_save_path/sess_$id";
  return (string) @file_get_contents($sess_file);
}

function write($id, $sess_data)
{
  global $sess_save_path;

  $sess_file = "$sess_save_path/sess_$id";
  if ($fp = @fopen($sess_file, "w")) {
    $return = fwrite($fp, $sess_data);
    fclose($fp);
    return $return;
  } else {
    return(false);
  }

}

function destroy($id)
{
  global $sess_save_path;

  $sess_file = "$sess_save_path/sess_$id";
  return(@unlink($sess_file));
}

function gc($maxlifetime)
{
  global $sess_save_path;

  foreach (glob("$sess_save_path/sess_*") as $filename) {
    if (filemtime($filename) + $maxlifetime < time()) {
      @unlink($filename);
    }
  }
  return true;
}

session_set_save_handler("open", "close", "read", "write", "destroy", "gc");

session_start();

// proceed to use sessions normally

?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <warning>
   <para>
    Write and Close handlers are called after destructing objects since PHP
    5.0.5. Thus destructors can use sessions but session handler can't use
    objects. In prior versions, they were called in the opposite order. It
    is possible to call <function>session_write_close</function> from the
    destructor to solve this chicken and egg problem.
   </para>
  </warning>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member>
     The <link linkend="ini.session.save-handler">session.save_handler</link>
     configuration directive
    </member>
   </simplelist>
  </para>
 </refsect1>
 
</refentry>

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