a confusion about php funtions

[UK-1991]

Hello,

I am confused about the php there is used to include a file like headers footers functions etc etc so I would like to ask what is the difference between the followings:
require_once();
require();
include();
include_once();

Thank You

This is php 101. http://php.net/manual/en/function.require.php

The once types ensure the file is only included or required once.

[UK-1991]

okay liek if I write require_once the file will be included once and if i include the file using require statement both will do the same am i right ?

Whether to include or require is a matter for you. I very rarely if ever use 'include' these days as most of the files I include are mandatory to the functioning of my app/page and are 'required'.
Using the _once constructs ensures that the file is only ever included/required once, even if there are multiple instances of including/requiring that file. My sites are not usually convoluted enough to demand the _once, but some seasoned php-heads insist that require_once is the only construct that should be used, ever. I can't say I'm totally convinced by this, as it may increase the time taken for code to run (may be marginal) over a stright require.

If you search long enough, you'll come across some examples of when to use which option. Again, many of these examples are largely subjective and open to argument.

[UK-1991]

Okay perfect my concept is cleared about 60% well I will se the examples as per your guidance

Great. So in short, my recommendation would be to use "require" as a rule. The "require_only" can be handy if you have a lot of nested requires with references to the same require files.

[Taywin]

This post is talking about performance difference between require and require_once. May be interested for you.