Sessie in database

<?php
class SessionManager {
   var $life_time;
   function SessionManager() {
      // Read the maxlifetime setting from PHP
      $this->life_time = get_cfg_var("session.gc_maxlifetime");
      // Register this object as the session handler
      session_set_save_handler( 
        array( &$this, "open" ), 
        array( &$this, "close" ),
        array( &$this, "read" ),
        array( &$this, "write"),
        array( &$this, "destroy"),
        array( &$this, "gc" )
      );
   }
}

function open( $save_path, $session_name ) {
        global $sess_save_path;
        $sess_save_path = $save_path;
        // Don't need to do anything. Just return TRUE.
        return true;
     }

function close() {
        return true;
}

function read( $id ) {
           // Set empty result
           $data = '';
           // Fetch session data from the selected database
           $time = time();
           $newid = mysql_real_escape_string($id);
           $sql = "SELECT `session_data` FROM `sessions` WHERE `session_id` = '$newid' AND `expires` > $time";
           $rs = db_query($sql);                           
           $a = db_num_rows($rs);
           if($a > 0) {
             $row = db_fetch_assoc($rs);
             $data = $row['session_data'];
           }
                       return $data;
}

function write( $id, $data ) {
         // Build query                
         $time = time() + $this->life_time;
         $newid = mysql_real_escape_string($id);
         $newdata = mysql_real_escape_string($data);
         $sql = "REPLACE `sessions` (`session_id`,`session_data`,`expires`) VALUES('$newid', '$newdata', $time)";
         $rs = db_query($sql);
         return TRUE;
}

function destroy( $id ) {
         // Build query
         $newid = mysql_real_escape_string($id);
         $sql = "DELETE FROM `sessions` WHERE `session_id` = '$newid'";
         db_query($sql);
         return TRUE;
}

function gc() {
         // Garbage Collection
         // Build DELETE query.  Delete all records who have passed the expiration time
         $sql = 'DELETE FROM `sessions` WHERE `expires` < UNIX_TIMESTAMP();';
         db_query($sql);
         // Always return TRUE
         return true;
}


?>