Question: What are the differences between require and include‚ include_once?

Question: What are the differences between require and include‚ include_once?
Answer:
require_once()‚include_once() both the functions include and evalute the specified file only once and if the specified file is opened previous to the present call occurrance‚ it will not be done again. But require() and include() will do it as many times they are asked to do. The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement‚ with the only difference being that if the code from a file has already been included‚ it will not be included again. The major difference between include() and require() is that in failure include produces a warning message whereas require produces a Fatal errors.