public static function prefixKeys( $prefix, array $data = array() )
    {
        foreach ( static::clean( $data ) as $_key => $_value )
        {
            if ( is_numeric( $_key ) )
            {
                continue;
            }

            if ( is_array( $_value ) )
            {
                $_value = static::prefixKeys( $prefix, $_value );
            }

            $data[$prefix . $_key] = $_value;
            unset( $data[$_key] );
        }

        return $data;
    }