How to override the ['search_distance'] in Location: Distance / Proximity Views in a custom module After looking at the location module. I couldn't find any way to override the 'search_distance' parameter by creating a custom Form. 

dose anyone know how to override this variable by using a custom module? .

I do have a map that is already searching proximity by zip code. it uses php code to determine the  latitude, longitude.

I want to add the 'distance' selectbox next to the zipcode and filter it by (25 miles, 50 miles, 100 miles) like that. 

Please note: the below Form for filtering is written in a custom module. so I'm looking for php code.
I haven't had much experience with Location module. This feature is supported out of the box with Openlayers module. I would recommend checking out that module.

I have done a similar sort of thing for one of my clients. I had to hide the distance fields as they didn't want that. If you view source you can see those fields in HTML.

http://biopetonline.com.au/stores