Is there any benefits for using include_once instead of include?

EPJS

Would I save any bandwidth or anything using include_once() instead of include()?

I've been using include() for about 1 1/2 years for things like masthead and footer copyright. But recently I've been switching some pages to include_once()

I really don't notice a difference between the two other than "include once only includes a file one time". I'm not even 100% sure what that means 😕

bpat1434

Well, you know the difference already. You said it:
include_once() only includes the file once.

If you use include() and include the same file multiple times in your script (not between refreshes) and you "reset" variables and what not (in the included file), then it's possible that the include will "overwrite" your variables.

If you use include_once() and include the same file multiple times, it won't include it again. So you "preserve" your variables and what not.

Usually it's safer to use include_once just so you know that if you call it again later, nothing will be "reset" to the default of your script. I honestly use include_once exclusively. I've lost my need for include() (for now) but I'm sure there are good reasons for it (like recursive functions).

One good example is including a file that declares a function. If you use include() multiple times, you'll get an error saying you can't redeclare the function. Using include_once() circumvents that. Help you understand?

EPJS

Ok thanks 🙂
Yeah I understood that.

I was confused before because for some reason I though a page reload counted as asking for the file again. Silly me :p

Your post makes sense 🙂 I guess I'll just stick with include_once()

Thanks 🙂

Doug_G

And btw, since include happens server-side, using include or include_once has no impact at all on your site bandwidth.

Drakla

And if you define functions or constants in the includes you won't get the old "You can't redeclare that function - wehh wehh!" screeching from php

MarkR

Sometimes you may want to do recursive includes. It depends really what your model of includes is.

We normally just include everything in a master include file, but this is not the only way of doing it.

If you explicitly include things, then you may have dependencies.

Suppose you have:

utils.php # no dependencies
htmlutils.php # depends on utils.php
dateutils.php # no dependencies
dbutils.php # depends on utils.php and dateutils.php

If I chose to include both htmlutils.php and dbutils.php, with a simple require() (Note 1), then they simply got utils.php with require() themselves, it would fail because utils.php had been included twice.

Therefore, I'd use require_once to do my includes.

Note 1: I ALWAYS use require() rather than include(), because it forces a fatal error if the file is missing, which prevents any possibilty that the script will charge headlong into oblivion, screwing things up as it goes.

Mark