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determining the application root path and url in php

December 13, 08 by Gabi Solomon

If you buid any web application you will eventually need to find a way to specify the application root path and URL. This is inevitable if you don't build your links in a relative way ( by unsing ./ and ../ combinations ), and also if you want to have a way of keeping things organized and working even if you move script to a new server or in a folder.

Well there are several ways you can do this. The first one would be to write them in a config file by hand, and edit them as you move the project.

PLAIN TEXT
PHP:
  1. define('ROOT_PATH', '/home/user/public_html/folder/');
  2. define('PROJECT_DIR', '/folder/');
  3. define('BASE_URL', 'http://' . $_SERVER['HTTP_HOST'] . PROJECT_DIR);

But even if that works well, it will give a bit of work when you move the application since you have to edit them by hand.
So the next method would be to have them be generated automatically. The ROOT_PATH is relatively easy to determine . What i do is have a directory called config in wich i place my config files, in it i have one called main_config.php which includes the rest of the config files. One of them is called paths.php.
Now to determine the root_path i use a function called dirname() and the __FILE__ constant.

PLAIN TEXT
PHP:
  1. define('ROOT_PATH', dirname(dirname(__FILE__)));
  2. define('PROJECT_DIR', '/folder/');
  3. define('BASE_URL', 'http://' . $_SERVER['HTTP_HOST'] . PROJECT_DIR);

Now we have the root_path solved and base_url to some extend, but need to specify the project directory.
We can solve that too automatically.

PLAIN TEXT
PHP:
  1. define('ROOT_PATH', '/home/user/public_html/folder/');
  2. $projectDir = implode('/', array_intersect(explode('/', $_SERVER["REQUEST_URI"]), explode('/', str_replace('\\', '/', ROOT_PATH))));
  3. if ($projectDir[strlen($projectDir)-1] != '/') {
  4.         $projectDir .= '/';
  5. }
  6. define('PROJECT_DIR', $projectDir);
  7. define('BASE_URL', 'http://' . $_SERVER['HTTP_HOST'] . PROJECT_DIR);

What that code does is take the ROOT_PATH that we defined and the REQUEST_URI from the server global variable and do an intersection of them to determine the project dir.

Hope this small snippet helped you.
Cheers