<?php

class crypt {

    private $skey;

    public function __construct($key) {
        $this->skey = hash("md5", $key, true); //32位skey
    }

    public function safe_b64encode($string) {
        $data = base64_encode($string);
        $data = str_replace(array('+', '/', '='), array('-', '_', ''), $data);
        return $data;
    }

    public function safe_b64decode($string) {
        $data = str_replace(array('-', '_'), array('+', '/'), $string);
        $mod4 = strlen($data) % 4;
        if ($mod4) {
            $data .= substr('====', $mod4);
        }
        return base64_decode($data);
    }

    public function encode($value) {
        if (!$value) {
            return false;
        }
        $text = $value;
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $this->skey, $text, MCRYPT_MODE_ECB, $iv);
        return trim($this->safe_b64encode($crypttext));
    }

    public function decode($value) {
        if (!$value) {
            return false;
        }
        $crypttext = $this->safe_b64decode($value);
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $decrypttext = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $this->skey, $crypttext, MCRYPT_MODE_ECB, $iv);
        return trim($decrypttext);
    }

}