PHP Encrypt/Decrypt: Simple class to encrypt url data

Encryption is useful where critical data is being transferred in url. I have found a simple and secure encryption class with some changes to make it fit for new users. You can use it in Codeigniter websites as well. Just copy it in application/libraries directory and use it in other libraries style.
Here is the code for encryption class.

Code:: class Encryption {
var $skey = "SuPerEncKey2010"; // you can change it

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);
}
}

credits:http://www.99points.info/2010/06/php-encrypt-decrypt-functions-to-encrypt-url-data/