canon picturestyle decode

<?php

function read_as_byte($filename){
    $handle = fopen($filename, "rb");
    $fsize = filesize($filename);
    $contents = fread($handle, $fsize);
    $byteArray = unpack("C*",$contents);
    return $byteArray;
}
function saveFile($a, $fn){
    $str = "";
    foreach($a as $k){
        $str.=chr($k);
    }
    $fp = fopen($fn,'w');
    fwrite($fp,$str);
    fclose($fp);
}

$dec_key = read_as_byte("./canon_ps.key");
$enc_file = read_as_byte("./PictureStyle.pf2");

$i = -11;
$dec = array();

foreach($enc_file as $ef){
    if($i>-1){
        $dec[] = $ef^$dec_key[$i];
        $i = $i%(512*513);
    }
    else
    {
        $dec[] = $ef;
    }
    $i++;
}
saveFile($dec, "./PictureStyle.decoded.pf2");