difference between require_once(), require(), include()

[matrixinfologics]

What is difference between require_once(),   require(), include(). all the  three function usely use to call a file in another file. what is the basic difference?

[Irate]

require_once() requires a file to be loaded only once so that no redirect loops occur and, like require(), it requires the file referenced to exist, otherwise it throws a fatal error and the script breaks.

include() and include_once() work analog to require_once() and require_once(), just that script parsing is not stopped if the file is not found (it'll display a warning E_NOTICE, though).

[xenLiam]

Simply put,

• require() - Includes a file. If it encountered an error including the file, it will display an error and stop execution.
• require_once() - Does a require() but if the file is already included, it will no longer include it and won't produce a loop of errors.
• include() - Includes a file. If it encountered an error including the file, it will display an error and continue executing the rest of the script (unsafe).
• include_once() - Does an include() but if the file is already included, it will no longer include it and won't produce a loop of errors.