gistfile1.php

<?php
App::uses('Component', 'Controller');

class CodeComponent extends Component {

	private $letters = array(
		'6','M','Z','J','L',
		'K','2','H','R','W',
		'5','U','3','S','Y',
		'X','4','7','C','A',
		'P','F','9','0','1'
	);

	public function encode($num) {
		$t = (int) $num;
		if ($t < 0)
			$t = 0;
		$len = count($this->letters);
		$code = '';
		do {
			$code = $this->letters[$t % $len] . $code;
			$t = (int) ($t / $len);
		} while ($t > 0);
		return $code;
	}

	public function decode($code) {
		if (empty($code)) {
			return false;
		}
		$num = 0;
		$len = count($this->letters);
		$codelen = strlen($code);
		for ($i=$codelen-1; $i >= 0; $i--) {
			$index = array_search($code[$i], $this->letters);
			if ($index === false)
				return false;
			$num += $index * pow($len, $codelen-$i-1);
		}
		return $num;

	}
}