validate server side part4a
[Note: Video ends prematurely; the last 9min are in part-4b.]
Pull the four top-level validation statements into their own function `allErrorMessages`. This way, all validation is pulled to approx. one single line in the handler: `echo toUL( allErrorMessages($_POST))`. Make test-cases for that function (borrowing -- but not replacing -- the handler-test-N files already developed).
A brief discussion of why we have so many %@#&*'in files.
