thorsten / phpMyFAQ

		$fcs = 0x07FF; // Frame Check Sequence

		// do most significant byte skipping the 2 most significant bits

		$data = hexdec($code_arr[0]) << 5;

		for ($bit = 2; $bit < 8; ++$bit) {

			if (($fcs ^ $data) & 0x400) {

				$fcs = ($fcs << 1) ^ $genpoly;

			} else {

				$fcs = ($fcs << 1);

			}

			$fcs &= 0x7FF;

			$data <<= 1;

		}

		// do rest of bytes

		for ($byte = 1; $byte < 13; ++$byte) {

			$data = hexdec($code_arr[$byte]) << 3;

		// do rest of bytes

		for ($byte = 1; $byte < 13; ++$byte) {

			$data = hexdec($code_arr[$byte]) << 3;

			for ($bit = 0; $bit < 8; ++$bit) {

				if (($fcs ^ $data) & 0x400) {

					$fcs = ($fcs << 1) ^ $genpoly;

				} else {

					$fcs = ($fcs << 1);

				}

				$fcs &= 0x7FF;

				$data <<= 1;

			}

		}

		return $fcs;

	}