Simple XOR obfuscator

xor_obfuscator.php

<?php

function xor_obfuscator ($string) {
    if (!strlen($string)) {
        return $string;
    }
    
    $key = ord($string{0});
    $new = pack("C",
        ($key & 0xf0)
        |
        (
            ($key & 0x0f)
            ^
            (($key >> 4) & 0x0f)
        )
    );
    
    for ($c=1;$c<strlen($string);$c++) {
        $new .= pack("C",ord($string{$c}) ^ $key);
    }
    
    return base64_encode($new);
}

function xor_deobfuscator ($string) {
    $string = base64_decode($string);
    
    if (!strlen($string)) {
        return $string;
    }
    
    $keys = unpack("C*",$string);
    $key = $keys[1];
    
    $key = ($key & 0xf0)
        |
        (
            ($key & 0x0f)
            ^
            (
                ($key >> 4)
                &
                0x0f
            )
        );
    
    $new = chr($key);
    
    for ($c=2;$c<=count($keys);$c++) {
        $new .= chr($keys[$c] ^ $key);
    }
    
    return $new;
}