php to base 62 - from base 62

gistfile1.php

/**
 * src - http://stackoverflow.com/questions/4964197/converting-a-number-base-10-to-base-62-a-za-z0-9
 */
class Base62 {

    public static $table = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

    public static function encode($num) {
        $base  = 62;
        $table = self::$table;

        $rest   = $num % $base;
        $return = $table[$rest];
        $floor  = floor($num / $base);
        while ($floor) {
            $rest   = $floor % $base;
            $floor  = floor($floor / $base);
            $return = $table[$rest] . $return;
        }

        return $return;
    }

    public static function decode($num) {
        $base  = 62;
        $table = self::$table;
        $limit = strlen($num);
        $res   = strpos($table, $num[0]);
        for ($i = 1; $i < $limit; $i++) {
            $res = $base * $res + strpos($table, $num[$i]);
        }

        return $res;
    }
}