String encryption with password

While searching for some thing, I found a string encryption code sample for Visual Basic, and I just wanted the same in php, and did a port. Just like what F. Balena has done over there, this function is also used for both, encrypt as well as decrypt.


<?php
function stringEncrypt($str, $pass){
    $strlen = strlen($str);
    $passIndex = 0;
    $passLen = strlen($pass);
    // null passwords wont encode
    if(strlen($pass) == 0) 
        return $str;
    for ($i = 0; $i < $strlen; $i++){
        // get the next char in the password
        $passChr = ord($pass[($i % $passLen)]);
        // encrypt one character in the string
        $str[$i] = chr(ord($str[$i]) ^ $passChr);
        // modify the character in the password (avoid overflow)
        $pass[($i % $passLen)] = chr(($passChr + 17) & 255);
    }
 return $str;    
}