Account for too few parameters

[dynamiccookies]

When no parameters are sent, the following error happens:
PHP Fatal error: Uncaught ArgumentCountError: Too few arguments to function decodeVIN(), 0 passed in

Just need to test for existence of $vin and return false; on failure.

[dynamiccookies]

Could make $vin optional by setting it to null if it doesn't exist. Then test for null and return custom error message if true.