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

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<refentry xmlns="http://docbook.org/ns/docbook" xml: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>
       Open function, this works like a constructor in classes and is 
       executed when the session is being opened. The open function 
       expects two parameters, where the first is the save path and 
       the second is the session name.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>close</parameter></term>
     <listitem>
      <para>
       Close function, this works like a destructor in classes and is 
       executed when the session operation is done.
      </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>
       The destroy handler, this is executed when a session is destroyed with 
       <function>session_destroy</function> and takes the session id as its 
       only parameter.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>gc</parameter></term>
     <listitem>
      <para>
       The garbage collector, this is executed when the session garbage collector 
       is executed and takes the max session lifetime as its only parameter.
      </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>
    As of PHP 5.0.5 the <parameter>write</parameter> and
    <parameter>close</parameter> handlers are called after object
    destruction and therefore cannot use objects or throw exceptions.
    The object destructors can however use sessions.
   </para>
   <para>
    It is possible to call <function>session_write_close</function> from the
    destructor to solve this chicken and egg problem.
   </para>
  </warning>
  <warning>
   <para>
    Current working directory is changed with some SAPIs if session is
    closed in the script termination. It is possible to close the session
    earlier with <function>session_write_close</function>.
   </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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