필요하신 분은 가져다 쓰세요.

class base62 {

	const $charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
	const $base = 62;

	public function encode($var) {
		$stack = array();
		while($var > 0) {
			$remainder = $var % self::$base;
			$var = (int)($var / self::$base);

			array_push($stack, self::$charset[$remainder]);
		}

		return implode('', array_reverse($stack));
	}

	public function decode($var) {

		$length = strlen($var);
		$result = 0;
		for($i=0; $i<$length; $i++) {
			$result += self::get_value($var[$i]) * pow(self::$base, ($length-($i+1)));
		}

		return $result;
	}

	private function get_value($var) {
		if(ereg('[0-9]', $var))
			return (int)(ord($var) - ord('0'));
		else if(ereg('[A-Z]', $var))
			return (int)(ord($var) - ord('A') + 10);
		else if(ereg('[a-z]', $var))
			return (int)(ord($var) - ord('a') + 36);
		else
			return $var;
	}
}
base62::encode(61);
base62::encode(128);
base62::encode(65536);
base62::encode(2147483647);

base62::decode(base62::encode(51));
base62::decode(base62::encode(255));
base62::decode(base62::encode(33232));
base62::decode(base62::encode(2047343643));
z
24
H32
2LKcb1

51
255
33232
2047343643