PHP: include & require, what is diff

Hope this is not stupid question.

I read the manual frequently, still could not understand what different between include() and require(), it makes no different to me.

Could you show me in an example script to show the different result between those two? Thanks.

I'm not really an expert, but I think include takes the script and inserts it into the new one, so if you included some HTML, and viewed the page source, you would simply see the HTML included, and require makes the script check say a config file to make the file work properly. Then again, I could be wrong.

To quote the PHP manual:

require() and include() are identical in every way except how they handle failure. They both produce a Warning, but require() results in a Fatal Error.

So, if you try to include a file that does not exist then a warning (technically E_WARNING) will be raised but the rest of the script is allowed to run through until the end. If you try to require a file which doesn't exist then a fatal error (E_ERROR) warning will be raised and the script will immediately stop.

Hope that clears things up a bit.

Spot on Salathe!

PHP provides four functions which enable you to insert code from other files.

* include()
* require()
* include_once()
* require_once()

All four can take a local file or URL as input. None of them can import a remote file. require() and include() functions are virtually similar in their function except for the way they handle an irretrievable resource. include() and include_once() provide a warning if the resource cannot be retrieved and try to continue execution of the program if possible. require() and require_once functions provide stop processing the page if they cannot retrieve the resource.

Why include_once() and require_once()
The include_once() and require_once() functions are handy in situations where multiple files may reference the same included code. For example:

File A.php includes File B.php and C.php
File B.php includes File C.php

File C.php has been included twice, so the interpreter would print an error. Since a function cannot be redefined once it’s declared, this restriction can help prevent errors.

If both File A.php and File B.php use include_once() or require_once() to import File C.php, no errors would be generated. PHP would understand that you only want one instance of the code in File C and would not try to redeclare the functions.

It is best to use require_once() to include files which contain necessary code and include_once() to include files that contain content which the program can run without e.g. HTML, CSS, etc.

Just to give the full story at once

Ref: Self Improvement