Why is it that facebook is coded in .php though it is such a complex interface?

Question

I came to know that the webpage of Facebook is basically on php and found it ridiculing.
I am not sure about the complexities of php.
Please enlighten me.

Answer 1

well someone told me that php webpages never hand or out of server load ? maybe its true as so many people use fb at same time but itis always smooth never server is down ?!?!?