What"s wrong with using $_REQUEST[]?

I've seen a number of posts on here saying not to use the $_REQUEST variable. I usually don't, but sometimes it's convenient. What's wrong with it?

Behaviour of final static method

I have been playing around with modifiers with static method and came across a weird behaviour.

Method Overloading. Can you overuse it?

What's better practice when defining several methods that return the same shape of data with different filters? Explicit method names or overloaded methods?

Does using method chaining in PHP cause any problems with resources or memory?

I'm talking about methods like this: