This is work in progress. I am not an expert on the topic by any means. Therefore, I have trouble finding and verifying information about common CRC algorithms. I am especially looking for reliable test vectors.

• CRC1
• CRC16, CRC16-CCITT, CRC16-DNP, CRC16-Modbus, CRC16-QT, CRC16-USB, CRC16-XModem, CRC16-ZModem

<?php

// Autoloading via Composer
require __DIR__ . '/vendor/autoload.php';

$crc16ccitt = new mermshaus\CRC\CRC16CCITT();

$crc16ccitt->update('Hello');
$crc16ccitt->update(' World!');

$checksum = $crc16ccitt->finish();

var_dump(bin2hex($checksum)); // string(4) "882a"

$ phpunit

• This library is mostly a port of Digest CRC for Ruby by Hal Brodigan.

• Digest CRC. The Ruby library on which this library is based.
• pycrc. A tool for generating C code and corresponding lookup tables for diverse CRC algorithms. Used by Digest CRC.
• CRC calculation. An online calculator to generate checksums for arbitrary polynomials and input. Recommended by pycrc.
• On-line CRC calculation and free library. Another online calculator for some CRC algorithms.
• Catalogue of parametrised CRC algorithms. Information about many different CRC algorithms.