將 Int 和 BigInt 型別數值轉換為字串的可逆方法，可用於縮短網址或記錄的ID轉換等。
如： 9223372036854775807 => aZl8N0y58M7

class Convert
{
    /**
     * 預設金鑰字串
     * @var string
     */
    const KEY = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    /**
     * 將 Int 型別十進位制數值轉換為指定進位制編碼
     * @param int|string $num 取值範圍 0 ~ 2147483647 之間
     * @return
 
 string
     */
    public static function encodeInt($num) {
        $str = '';
        if ($num <= 0)
            $str = substr(self::KEY, 0, 1);
        while ($num > 0) {
            $val = intval($num / 62);
            $mod = $num % 62;
            $str = substr(self::KEY, $mod, 1) . $str;
            $num
 
 = $val;
        }
        return $str;
    }

    /**
     * 將編碼字串轉換為 Int 類整型數值
     * @param string $code
     * @return int
     */
    public static function decodeInt($code){
        $result = null;
        $len = strlen($code);
        for ($i = 1; $i <= $len; $i++) {
            $char = substr($code
 
, $i - 1, 1);
            $result += intval(strpos(self::KEY, $char)) * pow(62, $len - $i);
        }
        return $result;
    }

    /**
     * 支援15位長度的整型，超過則精度大幅降低
     * @param int $num
     * @return string
     */
    public static function encodeInt2($num) {
        $out = '';
        for ($t = floor(log10($num)/log10(62)); $t >= 0; $t--) {
            $a = floor($num/bcpow(62, $t));
            $out = $out . substr(self::KEY, $a, 1);
            $num = $num - $a * pow(62, $t);
        }
        return $out;
    }

    /**
     * 支援最大15位整型字串的解碼
     * @param string $num
     * @return string
     */
    public static function decodeInt2($num) {
        $out = 0;
        $len = strlen($num) - 1;
        for ($t = 0; $t <= $len; $t++) {
            $out = $out + strpos(self::KEY, substr( $num, $t, 1 )) * pow(62, $len - $t);
        }
        return $out;
    }

    /**
     * 將 BigInt 型別的數值轉換為指定進位制值
     * @param int|string $num
     * @return string
     */
    public static function encodeBigInt($num) {
        bcscale(0);
        $str = '';
        if ($num <= 0)
            $str = substr(self::KEY, 0, 1);
        while ($num > 0) {
            $div = bcdiv($num, 62);
            $mod = bcmod($num, 62);
            $str = substr(self::KEY, $mod, 1) . $str;
            $num = $div;
        }
        return $str;
    }

    /**
     * 將編碼字串轉換為 BigInt 類整型數值
     * @param string $code
     * @return string
     */
    public static function decodeBigInt($code) {
        bcscale(0);
        $result = '';
        $len = strlen($code);
        for ($i = 1; $i <= $len; $i++) {
            $char = substr($code, $i - 1, 1);
            $result = bcadd(bcmul(strpos(self::KEY, $char), bcpow(62, $len - $i)), $result);
        }
        return $result;
    }
}

測試方法：

結果：

echo 'Begin ~~<br><hr><br>';
$begin = microtime(true);
$bm = memory_get_usage();

$j = 0;
$cv = new Convert();
//for ($i = 0; $i < 10000; $i++) {
    $raw = '9223372036854775807';//rand(200000, 214748) . rand(1000, 3648);
    $encode = $cv->encodeBigInt($raw);
    $decode = $cv->decodeBigInt($encode);
//    $encode = $is->encodeInt($raw);
//    $decode = number_format($is->decodeInt($encode), 0, '', '');
    if ($raw != $decode) {
        $j++;
//        echo '<script>alert("not same");</script>';
    }
//}
    echo '原文: '. $raw .' 長度: '. strlen($raw) .'<br>';
    echo '編碼: '. $encode .' 長度: '. strlen($encode) .'<br>';
    echo '解碼: '. $decode .'<br>';
echo '不一致：'. $j;
echo '<br>';

$em = memory_get_usage();

echo 'End !<br><hr><br>Use Time :';
echo microtime(true) - $begin;
echo '<br><hr><br>Use Mem:';
echo ceil(($em - $bm)/1024/1024) .'MB';