Mine would definitely have to be spelling of variables. Here is my story.
MY First Rule of Coding: WATCH FOR SPELLING.
My first bug was that I was going to... register.php?referall=1
I spelled referral wrong so I was getting back an empty text value.
Then I forgot to add in the &id so it would:
So yeah, after I got the CORRECT URL... the data started sending through and EVEN THEN it's still scary to look at.
My referral script does the following: If being referred by ID... take that ID, your ID, your IP, their IP and store it in the database.
Then let's say the referred user is referring someone else... well we their the referrer's ID, referrer referrer's ID, referrer's IP, and referrer referrer's IP. Then we do the appropriate cookie given.
I also check when the referrer has validated and registered their account. There is also code for checking input length, regex, captcha.. all that good stuff.
In fact... here is what I have so far:
So... what's your coding weakness?