Reverse the lame home-rolled 'encryption' someone posted

StupidDecode.php

<?php

// supplied encoding function
function stupidEncode($input, $key) {
	$k = $key;
	$r = $input;
	$l = strlen($r);
	$e = "";
	
	for($i=0; $i < $l; $i++){
		$s = dechex(ord(substr($key, $i%strlen($key), 1)));
		$c = dechex(ord(substr($r, $i, 1)));
		$x = bin2hex(pack('H*',$s) ^ pack('H*',$c));
		$e = $e."&#x".$x.";";
	}
	return $e;
}

// derived reversal
function stupidDecode($input, $key) {
	$parts = str_split($input, 6);
	$parts = array_map(function($a){return substr($a,3,2);}, $parts);
	$parts = array_map('hex2bin', $parts);
	$encstr = implode('', $parts);
	$out = '';
	for($i=0, $l=strlen($encstr); $i<$l; $i++) {
		$s = dechex(ord(substr($key, $i%strlen($key), 1)));
		$chr = $encstr[$i] ^ pack('H*',$s);
		$out .= $chr;
	}
	return $out;
}

// test
$input = 'Hello world!';
$key = 'foobar';

printf("Raw: %s\nKey: %s\n", $input, $key);
$en = stupidEncode($input, $key);
printf("Encoded: %s\n", $en);
$de = stupidDecode($en, $key);
printf("Decoded: %s\n", $de);

/* output:
Raw: Hello world!
Key: foobar
Encoded: &#x2e;&#x0a;&#x03;&#x0e;&#x0e;&#x52;&#x11;&#x00;&#x1d;&#x0e;&#x05;&#x53;
Decoded: Hello world!
*/