When would a script be included twice in PHP? [duplicate]

Question

I know that include_once and require_once will only allow the called script to run once. My question is this: If I don't use _once, would it always run multiple times? Does it run more than once by default? I searched for answers, but I found none.

Answer 1

include runs one time every time you write it. The point of using include_once is that you can do

include "myfile.php"; // Include file one time
include "myfile.php"; // Include file again

This is perfectly legal, and in some cases you would want to do that.

The problem is that if you for example define a function in this file, php complains that you can't define that method more than once (because the name is already taken).

include_once makes sure that the same file is not included more than once, so if you do:

include_once "myfile.php"; // Include the file one time
include_once "myfile.php"; // This is ignored

...Only one include is performed.

Answer 2

It's not that it runs multiple times, but if you had a file that included multiple different things and one of those thigns includes one of the other already included things you'd have them being included multiple times, which could be bad.