private function check_username($username) { $return = ''; if ($username == '') { $return .= 'Username cannot be left blank.<br />'; } if (User::check_alphanumeric($username) != TRUE) { $return .= 'Username must only contain letters and numbers.<br />'; } if (User::check_username_available($username) != TRUE) { $return .= 'Username not available.<br />'; } return strlen($return) > 0 ? $return : TRUE; }