public static function decodeZookoToByteStr($encodedStr) {
        // Check input string.
        $pattern = '/[a-km-uw-z13-9]*/';
        self::_checkEncodedString($encodedStr, $pattern);

        // Get length (byte count) of encoded string.
        $encodedStrLen = self::_byteCount($encodedStr);

        // Add padding character to mapping.
        $mapping = self::$_zookoFlippedAlphabet + array('_' => 0);

        // Get decoded byte-string.
        $byteStr = self::_decodeToByteStr($encodedStr, $encodedStrLen, $mapping, '_', true);
        
        // Return byte-string.
        return $byteStr;
    }