将 Int 和 BigInt 类型数值转换为字符串的可逆方法，可用于缩短网址或记录的ID转换等。

如： 9223372036854775807 => aZl8N0y58M7

class Convert

{

    /**

     * 默认密钥字符串

     * @var string

     */

    const KEY = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    /**

     * 将 Int 类型十进制数值转换为指定进制编码

     * @param int|string $num 取值范围 0 ~ 2147483647 之间

     * @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;

    }

    /**

     * 将编码字符串转换为 Int 类整型数值

     * @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;

    }

    /**

     * 支持15位长度的整型，超过则精度大幅降低

     * @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;

    }

    /**

     * 支持最大15位整型字符串的解码

     * @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;

    }

    /**

     * 将 BigInt 类型的数值转换为指定进制值

     * @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;

    }

    /**

     * 将编码字符串转换为 BigInt 类整型数值

     * @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;

    }

}

测试方法：

结果：

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: '. $raw .' 长度: '. strlen($raw) .'<br>';

    echo '编码: '. $encode .' 长度: '. strlen($encode) .'<br>';

    echo '解码: '. $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';