I was working on a school project (which took 2 weeks) and I had an error which cost me 7 hours to solve.
I tried lots and lots of things, but after those 7 hours (so, at the end of the day) I finally found the error:
Code:
username = $_POST["username'];
Note that there's a " in front of username while there's a ' on the end.
I remember a lot of people staring at me while I was cursing...