Customized Session Handler can not work for PHP 5.1.6 and CentOS 5.5

Hi, All, System: CentOS 5.5; PHP version is 5.1.6. I met a strange problem associate with session_save_handler in current environment(The same code can work well in my local windows platform and ubuntu system). I just want to use a customized session save handler to be triggered, so that I can call my own logic to handling the session. The testing in local is pretty great but when migration to the VPS, it bring me the following error: Fatal error: session_start() [<a href='function.session-start'>function.session-start</a>]: Failed to initialize storage module: user (path: /tmp) The default value for session save handler and session save path in php.ini are: session.save_handler = files session.save_path = "/tmp" session.name = PHPSESSID And the bottom are the code for the session handler. I first called ob_start(), and after calling session::init(), I called session_start(). Then the fatal error happen. It did not trigger any function in the "session" class. I tried change the php.ini from session.save_handler = user, but the error remains. And I found no matter what session.save_handler type is, after calling session_set_save_handler(), the session.save_handler will always automatically changed to 'user', that's why the Fatal error info shows user (path: /tmp). Can anybody help me out for such error? I was stuck by this issue for more than 2 days, but still haven't get any clue! You can view more details from stackoverflow if you want. Here is the link: http://stackoverflow.com/questions/8845924/session-set-save-handler-class-for-database-not-working <?php class session { public static function init() {

    session_set_save_handler('session::open', 'session::close', 'session::read', 'session::write', 'session::destroy', 'session::gc');

} public static function open($save_path, $session_name) {

     if (!is_dir($save_path)) {
            mkdir($save_path, 0777);
     }
    return true;

} public static function close() {

    return true;

} public static function read($sid) {

    global $db, $user;
    register_shutdown_function('session_write_close');
    if (!isset($_COOKIE[session_name()])) {
      $user = anonymousUser($sid);
      return '';
    }
    $result = $db->query('SELECT s.data as session_data, s.* , u.* FROM users u INNER JOIN sessions s ON u.uid = s.uid WHERE s.sid = "' . $db->escape($sid) .
      '" AND timestamp >= ' . $db->escape(TIMESTAMP - Bl_Config::get('session.lifetime', 10800)));
    $user = $result->row();

    if ($user) {
      $data = $user->session_data;
      unset($user->passwd, $user->session_data);
      if ($user->uid > 0 && $user->status == 1) {
        $userInstance = User_Model::getInstance();
        $user->roles = $userInstance->getUserRoles($user->uid);
        $user->roles[] = User_Model::ROLE_AUTHENTICATED_USER;
        $user->permissions = array();
        $user->data = (isset($user->data) && $user->data) ? unserialize($user->data) : array();
        foreach ($user->roles as $rid) {
          $user->permissions = array_merge($user->permissions, $userInstance->getRolePermissions($rid));
        }
        $user->permissions = array_unique($user->permissions);
      } else {
        $user = anonymousUser($sid);
      }
      return $data;
    } else {
      $user = anonymousUser($sid);
      return '';
    }

} public static function write($sid, $data) {

    global $db, $user;
    if (!isset($user) || ($user->uid == 0 && empty($_COOKIE[session_name()]) && empty($data))) {
      return true;
    }
    $uri = '/' . Bl_Core::getUri();
    $db->exec('UPDATE sessions SET uid = ' . $db->escape($user->uid) . ', ip = "' . $db->escape(ipAddress()) .
      '", uri = "' . $db->escape($uri) . '", data = "' . $db->escape($data) . '", timestamp = ' .
      $db->escape(TIMESTAMP) . ' WHERE sid = "' . $db->escape($sid) . '"');
    if (!$db->affected()) {
      $db->exec('INSERT IGNORE INTO sessions (sid, uid, ip, uri, data, timestamp) VALUES ("' . $db->escape($sid) .
        '", ' . $db->escape($user->uid) . ', "' . $db->escape(ipAddress()) . '", "' . $db->escape($uri) . '", "' .
        $db->escape($data) . '", ' . $db->escape(TIMESTAMP) . ')');
    }
    return true;

} public static function destroy($sid) {

    global $db;
    $db->exec('DELETE FROM sessions WHERE sid = "' . $db->escape($sid) .. '"');
    return true;

} public static function gc($lifetime) {

    global $db;
    $db->exec('DELETE FROM sessions WHERE timestamp < ' . $db->escape(TIMESTAMP - Bl_Config::get('session.lifetime', 10800)));
    return true;

} public static function count($timestamp = 0, $hasAnonymous = true) {

    global $db;
    if (!$hasAnonymous) {
      $cond = ' AND uid > 0';
    } else {
      $cond = '';
    }
    $result = $db->query('SELECT COUNT(0) FROM sessions WHERE timestamp 
' . $timestamp . $cond);
    return $result->one();

} }