title: CRC_CCITT checksum PHP
body: <p>I have a problem with getting the right checksum of the hex CommandBlock I want to send to the controller.</p>
  
  <p>The existing code is in Deplhi, and I am not a good friend with Deplhi, so I want to do it in PHP. The array below is CommandBlock with the checksum (the last 2 bytes) which I have no idea how to get them:</p>
  
  <pre><code>$commandBlock = [0x10, 0x02, 0x42, 0x01, 0x02, 0x10, 0x03, **0xa3, 0xd9**];
  </code></pre>
  
  <p>The only thing I know is that there was used <em>CRC_CCITT()</em> function.</p>