Hello,
I made the same project as a sub-system for tracking student attendace inside a larger one.
I made a system that works as follows:-
1- Professors generate attendance codes (QR codes generated automatically by a click).
2- Professors open a page for students to scan the codes (The page automatically displays generated codes).
3- Students use their mobiles (Using FireFox) to scan QRCodes.
4- The system reads QRCodes and then registers the student as "attended".
I can let you try the system yourself.
=> I intensionlly made a low bid to attract my first FreeLancer customer, but generally, i am a PHP developer since 2008, and i use frameworks (Like CodeIgniter), but i don't mind to make this project in NativePHP if you want.