function calc($a, $b)
	{
		return ($a % $b + $b) % $b;
	}

	function cr($text, $key, $go)
	{
		$keyleght = strlen($key);

		for ($i = 0; $i < $keyleght; ++$i){
			if (!ctype_alpha($key[$i])){
				return "";
			}
		}
		$out = "";
		$fos = 0;
		$textleght = strlen($text);

		for ($i = 0; $i < $textleght; ++$i){
			if (ctype_alpha($text[$i])){
				$up = ctype_upper($text[$i]);
				$offset = ord($up ? 'A' : 'a');
				$keyind = ($i - $fos) % $keyleght;
				$k = ord($up ? strtoupper($key[$keyind]) : strtolower($key[$keyind])) - $offset;
				$k = $go ? $k : -$k;
				$ch = chr((calc(((ord($text[$i]) + $k) - $offset), 26)) + $offset);
				$out .= $ch;
			}else{
				$out .= $text[$i];
				++$fos;
			}
		}
		return $out;
	}

	function enc($text, $key) //encrypt
	{
		return cr($text, $key, true);
	}

	function dec($text, $key) //decrypt
	{
		return cr($input, $key, false);
	}