2-way php encryption (mcrypt)

2-way-crypt.php

#!/usr/bin/env php
<?php

class Coder
{
    const CRYPT_CIPHER = MCRYPT_RIJNDAEL_128;
    const CRYPT_MODE = MCRYPT_MODE_ECB;

    protected static function get_crypt_iv()
    {
        $sz = mcrypt_get_iv_size(static::CRYPT_CIPHER, static::CRYPT_MODE);
        $iv = mcrypt_create_iv($sz, MCRYPT_RAND);
        return $iv;
    }

    protected static function get_crypt_key($key)
    {
        $key = hash('md5', $key);
        return $key;
    }

    public static function encr($in, $key)
    {
        $iv = static::get_crypt_iv();
        $key = static::get_crypt_key($key);
        $out = mcrypt_encrypt(static::CRYPT_CIPHER, $key, $in, static::CRYPT_MODE, $iv);
        $out = base64_encode($out);
        return $out;
    }

    public static function decr($in, $key)
    {
        $iv = static::get_crypt_iv();
        $key = static::get_crypt_key($key);
        $in = base64_decode($in);
        $out = mcrypt_decrypt(static::CRYPT_CIPHER, $key, $in, static::CRYPT_MODE, $iv);
        $out = rtrim($out, "\0");
        return $out;
    }
}

$k = isset($argv[2]) ? $argv[2] : 'secret';
$p = isset($argv[1]) ? $argv[1] : 'passwd';

$ep = Coder::encr($p, $k);

$dp = Coder::decr($ep, $k);

var_dump($k, $p, $ep, $dp, $p === $dp);