WordPress get_query_var()

Question

I am busy developing a WordPress application and I need to be able to pass url parameters using WordPress functions. I use add_query_arg() function to add a url par

Answer 1

If you check out the Codex, you'll see you actually need to do some fiddling to get WP to start reading your query string.

Codex (under Custom Query Vars)

Excerpt:

In order to be able to add and work with your own custom query vars that you append to URLs (eg: "mysite com/some_page/?my_var=foo" - for example using add_query_arg()) you need to add them to the public query variables available to WP_Query. These are built up when WP_Query instantiates, but fortunately are passed through a filter 'query_vars' before they are actually used to populate the $query_vars property of WP_Query.