Diference between /../*.php and *.php

Question

So I had this trouble with a PHP code that I solved, but I don't really know how it works.

I tried to add this to every single file

<?php include '/nav.php'; ?>

So I can only have one file to edit the navbar instead of the whole php files.

The problem came up when I added that code to the files of another folder (ie. /general/vision.php) and I got an error (file not found). I though it was because I only hav the 'nav.php' file on the root of the site.

So, just for fun, I changed the sentence of the /general/vision.php file to

<?php include '../nav.php'; ?>

And it worked. I didn't changed the nav.php from the root, and it worked.

I'm glad it did, but I don't know why. How does that /../ works? Is that listed on the PHP documentation?

Answer 1

.. is OS nomenclature for "up a directory." It's nothing PHP specific.

Take a look at the concept of Relative paths.. might shed some light. Relative paths vs Absolute paths.

Answer 2

.. refers to the parent directory. This is pretty standard for all operating systems.

Answer 3

PHP is a server side scripting language, which means the root directory / is not the document root of your website, but the root of your filesystem on the server.

By beginning your path with / you are specifying an absolute path to the file, starting from the root. You can build a path relative from the current directory by using for example .. to ascend one level.

You can also build an absolute path using the __DIR__ constant in PHP, which always contains the full absolute path to the directory which contains the current PHP file, for example include __DIR__ . '/../nav.php';.

Answer 4

While you solved your problem by having .. (parent directory) in your include path, it is better to include the php file like this:

 include $_SERVER['DOCUMENT_ROOT']."/nav.php";

Then you can keep your PHP files anywhere in DOCUMENT_ROOT and will still be able to include this nav.php file.

PS: Its a good practice to keep common include files a level above DOCUMENT_ROOT so that these files cannot be directly accessed by browsers.