<?php

/**

 * 十进制数转换成62进制

 *

 * @param integer $num

 * @return string

 */

function from10_to62($num) {

    $to = 62;

    $dict = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    $ret = '';

    do {

        $ret = $dict[bcmod($num, $to)] . $ret;

        $num = bcdiv($num, $to);

    } while ($num > 0);

    return $ret;

}

/**

 * 62进制数转换成十进制数

 *

 * @param string $num

 * @return string

 */

function from62_to10($num) {

    $from = 62;

    $num = strval($num);

    $dict = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    $len = strlen($num);

    $dec = 0;

    for($i = 0; $i < $len; $i++) {

        $pos = strpos($dict, $num[$i]);

        $dec = bcadd(bcmul(bcpow($from, $len - $i - 1), $pos), $dec);

    }

    return $dec;

}