Why use output buffering in PHP?

Question

I have read quite a bit of material on Internet where different authors suggest using output buffering. The funny thing is that most authors argument for its use only becaus

Answer 1

Output buffering is critical on IIS, which does no internal buffering of its own. With output buffering turned off, PHP scripts appear to run a lot slower than they do on Apache. Turn it on and they run many times faster.