Encryption Decryption in PHP

<?php
/*
* Author: Zuh@ir
* Encryption Decryption in PHP
*/

$encrypt=encrypt("zuhair_mirza@yahoo.com", "testkey");

$decrypt=decrypt($encrypt, "testkey");

var_dump($encrypt,"2",$decrypt);

function encrypt($string, $key) {
$result = '';
for($i=0; $i<strlen($string); $i++) {
$char = substr($string, $i, 1);
$keychar = substr($key, ($i % strlen($key))-1, 1);
$char = chr(ord($char)+ord($keychar));
$result.=$char;
}

return base64_encode($result);
}

function decrypt($string, $key) {
$result = '';
$string = base64_decode($string);

for($i=0; $i<strlen($string); $i++) {
$char = substr($string, $i, 1);
$keychar = substr($key, ($i % strlen($key))-1, 1);
$char = chr(ord($char)-ord($keychar));
$result.=$char;
}

return $result;
}
?>