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Difference Between Include() Vs Include_once() In Php

Posted On Sun Dec 14, 2008 By wallpaperama In PHP Forums And Topics Discussions About Hyper Text Programming Language Forums

if you are reading my post you are here because you are probably wondering what are the differences between include() vs include_once() in php.

well, im going to try to explain.. this is the official explanation of include() vs include_once() per php.net:

Quote:

The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. As the name suggests, it will be included just once.

ok, what does this mean exactly? lets say for example, i have three files,

FILES:

FUNCTIONS.PHP
GLOBALS.PHP
HEADER.PHP

this is how each file looks like:

FUNCTIONS.PHP

<?php
function foo(){
echo 'some code';
}
?>

GLOBALS.PHP:

<?php
include('FUNCTIONS.PHP');
foo();
?>

HEADER.PHP

<?php
include('FUNCTIONS.PHP');
include('GLOBALS.PHP');
foo();
?>

now if you try to open HEADER.PHP you will get an error because GLOBALS.PHP includes FUNCTIONS.PHP already. you will get an error saying that function foo() was already declared in GLOBALS.PHP, and i also included in HEADER.PHP - which means i have included FUNCTIONS.PHP two times.

so to be sure i only include FUNCTIONS.PHP only ONE time, i should use the include_once() function, so my HEADER.PHP should look like this:

HEADER.PHP

<?php
include_once('FUNCTIONS.PHP');
include('GLOBALS.PHP');
?>

now when i open HEADER.PHP, i will not get an error anymore because PHP knows to include the file FUNCTIONS.PHP only ONCE

so to avoid getting an error, it would just be safe to use include_once() instead of include() function in your php code.

if you know you are messy with your PHP code, then its safer to use the include_once(), but if you keep track of all your code, then its ok to use the include() function.

hope i helped you explained the difrences between the include() and the include_once() functions in php

Vipul Mon May 06, 2013

It made very easy to understand !! Thanks a lot

Marejean Fri Apr 19, 2013

Thanks! :) It helps me alot! :)

saranya Sat Mar 23, 2013

It's very useful.Example too good for understanding.

shylaja Fri Mar 15, 2013

Thank u very much....It helps me a lot..thank u

Farid Wed Mar 06, 2013

Thank u very much, it was very helpful

Konst Tue Feb 26, 2013

Thank you very much very useful and clearly stated.

Bose Fri May 25, 2012

Thank you very much sir..

greatly Wed May 02, 2012

thanks it was easy to understand

ajit Tue May 01, 2012

nice examples. Helpfull one

rajiv Sat Apr 28, 2012

thanks sir

Heshan Wed Apr 25, 2012

Thanks mate :)

Ankita Tue Apr 24, 2012

I really satisfiedwid ur answer.
Thankyo

Oscar Fri Apr 20, 2012

in a nut shell ,thank you very much

jitendra Sun Apr 15, 2012

Thanks a lot ,for the nice example whit answer.........

Pete Thu Mar 29, 2012

Thanks, I have read several explanations on include and include_once, yours was by far the most concise and easy to understand.

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Difference Between Include() Vs Include_once() In Php

Title: Difference Between Include() Vs Include_once() In Php

Description: if you are reading my post you are here because you are probably wondering what are the differences between include() vs include_once() in php

Tags: difference ,between ,include ,vs ,include ,once ,in ,php

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Date: Sun Dec 14, 2008
Author wallpaperama Received 76 Replies #1222

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