What is inverse function to XOR?

The inverse is XOR! If you have: You can get a or b back if you have the other value available: For example if a = 5, b = 3 (and thus c = 6 as you mentioned) you get:

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)