How to set root folder for PHP include files

Question

I've spent days researching the internet and I can't find the answer that I will understand and are able to implement.

I've got the website in which I want to use include_once files and be able to view the website properly in both localhost and the actual server.

I've used $_SERVER['DOCUMENT_ROOT'] before but it doesn't work on the localhost so it is hard for me to update and do the changes to the website.

What I want to do is to create some sort of config.php file in which I can tell it that the root folder is either called htdocs or public_html and to "start" looking for files from there.

Or is there any other way I can get include paths to work?

I've seen replies with e.g. dirname(__FILE__), __DIR__, etc. but they never explained how it would work, where to write it in the code, etc. I'm a bit sick and tired of finding part of the answer and then running around in circles just try and "fill in" the gaps. I'm not a PHP expert, just trying to make my life a bit easier by using it.

Answer 1

dirname(__FILE__) and __DIR__ both same and __DIR__ comes with PHP 5.3

These are used in order to indicate that the "path of the file where they called".

URL: http://localhost/test/a.php

DIR: --NIX
     /var/www/test/a.php
     --WIN
     D:\lamp\www\test\a.php

// a.php's inside
<?php
echo __DIR__;

Gives you this on linux: /var/www/test

So, if you need a config parameter in all your project, just define it in your config.php and use it where you want both the file name that will be included.

./
  config.php
  index.php
  header.php
  footer.php
  /lib
    foo.php
  /tmp
    bar.php

./config.php define('ROOT', __DIR__ .'/');

./index.php include_once(ROOT .'header.php'); ... include_once(ROOT .'footer.php');

i.e, using it in tmp dir

./tmp/bar.php include_once(ROOT .'lib/foo.php');

UPDATE

// config.php
<?php
define("ROOT", __DIR__ ."/");

So, we use this for index.php to include banner.php and banner.php is waiting in ./banners/banner.php;

// index.php and the very first line!
<?php
include_once("config.php");
?>
// some html stuff
// ...
<?php include_once(ROOT ."banners/banner.php"); ?>
// some more html stuff
// ...

So, you should include config.php first to where you need it.

I think, this is basic as far as needed...

UPDATE

So your problem is not PHP include system, but question, anyway... :)

If your image path is changing (so not fixed), you can do like this;

// config.php
define("ROOT", __DIR__ ."/");
define("HTTP", ($_SERVER["SERVER_NAME"] == "localhost")
   ? "http://localhost/your_work_folder/"
   : "http://your_site_name.com/"
);

// banner.php
<img src="<?php print HTTP; ?>images/banner.gif">