The absolute path is sometimes required in application development. However it is adviced to use, where possible, a relative path.

example absolute path: /usr/local/pem/vhosts/102547/webspace/httpdocs/admin/myfile.php

example relative path: admin\myfile.php. (relative to the location where the request is done)

To be able to find your absolute path or document root folder you have to upload a small php file that looks as following:

<?php
phpinfo();
?>

Save this file as phpinfo.php and then use FTP program to upload this to your webhosting, or use the filemanager.

Then execute the php file and you will get a very long list with settings. Scroll down until you see Environment and you will be able to identify the DOCUMENT_ROOT or absolute path of your website.