Mkdir() in the absolute path

Question

I have a rather interesting question that seems simple to answer, yet I have searched and cannot find the proper answer. I am wanting to create a directory using mkdir() into the root directory of my website. How can this be done if the PHP file that I am using is inside a subdirectory folder (due to project constraints)?

I've tried several variations like putting a " . " before the directory name.

Thanks, drummer392

Answer 1

mkdir($_SERVER['DOCUMENT_ROOT']."/dir");