class email
{
  static function is_valid($str_email) 
  {
    if (!eregi('^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,4})$', $str_email)) { 
      return false;
    }
    return true;
  }
}