How to pass a parameters through URL? using PHP or JS

I used a store locator plus plugin and I have 3 Dropbox (built in). Now, I want to add another Dropbox (4th Dropbox). The third Dropbox will be cascaded to the 4th Dropbox. Let say, the 4th Dropbox is "items". When the user chooses a Mall (3rd Dropbox), the 4th Dropbox will display only the items that malls have.

How to do this?

Here's the link http://bit.ly/1NDAnQA

via Chebli Mohamed