Something

function decompress2($in_data, $out_len)
{
	$pos_max = strlen($in_data) - 1;
	$pos = -1;
	$out_data = '';

	do
	{
		$ctrl = ord($in_data[++$pos]);

		if ($ctrl > 31)
		{
			if ($ctrl < 0xE0)
			{
				$len = 2 + ($ctrl >> 5);
			}
			else
			{
				$len = 2 + ($ctrl >> 5) + ord($in_data[++$pos]);
			}

			$backref = (($ctrl & 0x1F) << 8) + 1 +  ord($in_data[++$pos]);

			if ($len <= $backref)
			{
				$out_data .= substr($out_data, -$backref, $len);
			}
			else
			{
				/**
				* If the length of the block is longer than the back ref, it means
				* that we're going to repeat the same pattern over and over
				*/
				$out_data .= str_pad('', $len, substr($out_data, -$backref), STR_PAD_RIGHT);
			}
		}
		else
		{
			$out_data .= substr($in_data, ++$pos, $ctrl + 1);
			$pos += $ctrl;
		}
	}
	while ($pos < $pos_max);

	if (isset($out_data[$out_len]))
	{
		die("WTF");
	}

	return $out_data;
}