PHP ID Encoder adding a slash

one text

Problem: I am using Opaque class to encode/decode IDs which works great, however after months when I submitted sitemaps to Google I realized that this class add a SLASH in IDs e.g. 173557 is converted to /eP/2Q ... now this has 2 slashes and when I open the url it works fine but Google Search Console gives me 404 error on this page, how can I fix this code not to include a . and a slash / in the encoded ID. Secondly, in Bing Webmaster Tools, all urls are small letters, but here I have Capital letter, Bing also gives 404 on thousands of urls which load fine for me.

Sorry for this question, I tried removing the '+/' from the code to fix my problem which didn't work. So, I had to ask if someone could help.

PHP Class on github: https://github.com/marekweb/opaque-id

Below is the code:

/**
 * Opaque ID encoder.
 *
 * Translates between 32-bit integers (such as resource IDs) and obfuscated
 * scrambled values, as a one-to-one mapping. Supports hex and base64 url-safe
 * string representations. Expects a secret integer key in the constructor.
 *
 * (c) 2011 Marek Z. @marekweb
 */
class OpaqueEncoder {

    private $key;
    private $extraChars = '.';
    
     const ENCODING_INT = 0;
     const ENCODING_HEX = 1;
     const ENCODING_BASE64 = 2;
    
    /**
     * @param $key Secret key used for lightweight encryption.
     */
    public function __construct($key, $encoding = self::ENCODING_HEX) {
        $this->key = $key;
        $this->encoding = $encoding;
    }
    
    /**
     * Produce an integer hash of a 16-bit integer, returning a transformed 16-bit integer.
     */
    protected function transform($i) {
        $i = ($this->key ^ $i) * 0x9e3b;
        return $i >> ($i & 0xf) & 0xffff;
    }
    
    /**
     * Reversibly transcode a 32-bit integer to a scrambled form, returning a new 32-bit integer.
     */
    public function transcode($i) {
        $r = $i & 0xffff;
        $l = $i >> 16 & 0xffff ^ $this->transform($r);
        return (($r ^ $this->transform($l)) << 16) + $l;
    }
    
    /**
     * Encode a value according to the encoding mode selected upon instantiation.
     */
    public function encode($i) {
        switch ($this->encoding) {
            case self::ENCODING_INT:
                return $this->transcode($i);

            case self::ENCODING_BASE64:
                return $this->encodeBase64($i);

            case self::ENCODING_HEX:
            default:
                return $this->encodeHex($i);
        }
    }
    /**
     * Decode a value according to the encoding mode selected upon instantiation.
     */
    public function decode($s) {
        switch ($this->encoding) {
            case self::ENCODING_INT:
                return $this->transcode($s);

            case self::ENCODING_BASE64:
                return $this->decodeBase64($s);

            case self::ENCODING_HEX:
            default:
                return $this->decodeHex($s);

        }
    }
    
    /**
     * Transcode an integer and return it as an 8-character hex string.
     */
    public function encodeHex($i) {
        return dechex($this->transcode($i));
    }
    
    /**
     * Transcode an integer and return it as a 6-character base64 string.
     */
    public function encodeBase64($i) {
        return strtr(substr(base64_encode(pack('N', $this->transcode($i))), 0, 6), '+/', $this->extraChars);
    }

    /**
     * Decode an 8-character hex string, returning the original integer.
     */
    public function decodeHex($s) {
        return $this->transcode(hexdec($s));
    }
    
    /**
     * Decode a 6-character base64 string, returning the original integer.
     */
    public function decodeBase64($s) {
        $unpacked = unpack('N', base64_decode(strtr($s, $this->extraChars, '+/')));
        return $this->transcode($unpacked[1]);
    }
}

I added the folloding in my functions.php

$encoder = new OpaqueEncoder(0x3b79db9a, OpaqueEncoder::ENCODING_BASE64);

For decoding I use:

$decoded_id = $encoder->decode($id);