I want to search a folder/directory on a client's computer when a button is pressed. Opendir seems to scan the path on the server and not the client. Can anyone confirm or deny this, and if it is possible how should I go about doing it?

Confirmed. Not possible with PHP, as it is a server-side script.

PHP is server-side. It can ONLY work with the directory structure on the server.

This sounds like something for a client-side language like javascript, but I imagine there are security restrictions in place in most/all browsers to prevent or hinder the ability to recurse through the user's harddrive. Can't say for sure off the top of my head.