If I understand you correctly, You have two folders, one houses your php script that you want to include into a file that is in another folder?
If this is the case, you just have to follow the trail the right way. Let's assume your folders are set up like this:
root
includes
php_scripts
script.php
blog
content
index.php
If this is the proposed folder structure, and you are trying to include the "Script.php" file into your "index.php" folder, you need to include it this way:
include("../../../includes/php_scripts/script.php");
The way I do it is visual. I put my mouse pointer on the index.php (looking at the file structure), then every time I go UP a folder, I type another "../" Then you have to make sure you go UP the folder structure ABOVE the folders that you want to start going DOWN into. After that, it's just normal folder hierarchy.