php - Get parent directory of running script

Question

In PHP, what would be the cleanest way to get the parent directory of the current running script relative to the www root? Assume I have:

$_SERVER['SCRIPT_NAME'] == '/relative/path/to/script/index.php'

Or just:

$something_else == '/relative/path/to/script/'

And I need to get /relative/path/to/ with slashes properly inserted. What would you suggest? A one liner is preferred.

EDIT

I need to get a path relative to the www root, dirname(__FILE__) gives me an absolute path in the filesystem so that won't work. $_SERVER['SCRIPT_NAME'] on the other hand 'starts' at the www root.

Answer 1

If your script is located in /var/www/dir/index.php then the following would return:

dirname(__FILE__); // /var/www/dir

or

dirname( dirname(__FILE__) ); // /var/www

---

Edit

This is a technique used in many frameworks to determine relative paths from the app_root.

File structure:

 /var/
      www/
          index.php
          subdir/
                 library.php

index.php is my dispatcher/boostrap file that all requests are routed to:

define(ROOT_PATH, dirname(__FILE__) ); // /var/www

library.php is some file located an extra directory down and I need to determine the path relative to the app root (/var/www/).

$path_current = dirname( __FILE__ ); // /var/www/subdir
$path_relative = str_replace(ROOT_PATH, '', $path_current); // /subdir

There's probably a better way to calculate the relative path then str_replace() but you get the idea.