function pop()
    {
        $err = @array_shift($this->_errors);
        if (!is_null($err)) {
            @array_pop($this->_errorsByLevel[$err['level']]);
            if (!count($this->_errorsByLevel[$err['level']])) {
                unset($this->_errorsByLevel[$err['level']]);
            }
        }
        return $err;
    }