How are input keys exploitable by malicious users?

Question

In the CodeIgniter PHP framework, there is a function that automatically runs on each request that, among other things, filters the GET/POST/COOKIE array keys, and kills the

Answer 1

Perhaps it is trying to prevent this attack.

The attack works by using knowledge of how PHP builds its hashing structures to make keys in $_POST which take an arbitrarily long time to process.

I suspect it is probably just trying to prevent the more mundane SQL injection attacks though.