PHP and zip codes

[monkeymade]

I am not sure if this is PHP or what, but I assume that it can be done using PHP along with something else.  What I am trying to figure out how to do, is figure the distances between zip codes.

I have seen this done on personals, ebay, and a plethra of other sites.  A form asks you to put in your zip code, and show results within x amount of miles.  This would be easy of course if I just had it search the database for anything within 50 or so zip codes, for example a 43611 code (my own) would bring back a 43659 zip code.  But just because they are within 50 zip codes of each other don't tell me the millage (in this case, its only 2.5 miles).

Maybe a soap method? I don't know, thats why I am here.  What can you guys tell me about this?

The way my database is going to be set up is that it will have usernames, passwords, and home addresses, including zip codes.  I want other members to be able to just enter a distance and find other members within that set distance.

Thanks for any help you can offer with this.....

[simcoweb]

This is done with longitude/latitude coordinates. These can be found in some free databases. Check at www.hotscripts.com under PHP / Zip Codes and you'll find them.