location based code...

kargrafx

I am curious how I would go about doing two things on a site I am thinking of creating...

First, is to have some code that detects where a user is based on their IP - I know this is not infallible, for numerous reasons, but it would be nice to have a zip code or city/state auto selected for the visitors and that is the only way I know to do it...

Second, along the same lines, is to have visitors able to search for members who are within a certain distance of them; say I want to find everyone in the same city or within 50 miles of my zip code, etc. I know this requires something more than just coding... but I don't know what/where/how to do that. I see it all over the internet, and I know not every site has manually entered a huge database of zip codes, cities, etc., and the distances from each other - so how do I go about that?

Thanks!

Crimsonfox

I imagine you'd need access to a database that contains ZIP/POSTAL codes.

Regarding distance between users, you might be able to make use of the Google Maps API. There's some interesting stuff in there regarding directions which gives distances.

bradgrafelman

Crimsonfox wrote:
I imagine you'd need access to a database that contains ZIP/POSTAL codes.

The US Census website actually provides this information in a CSV file here (look for the ZCTAs links - especially the "Record Layout"). This makes it quite easy to import the information automagically into your own DB using a simple 'LOAD DATA INFILE' MySQL query.

Crimsonfox wrote:
Regarding distance between users, you might be able to make use of the Google Maps API.

Actually, you can do this offline as well (e.g. no requests to external APIs) if you use something like the ZCTAs as linked above.

If you've got the latitude/longitude of two zip codes, you can find the distance between them using a simple point-distance formula for a sphere (as long as you assume that the Earth is perfectly spherical - which it isn't - and don't mind the slight error introduced in doing so).

You can Google for more info/formulas, but this site explains the gist of what I'm talking about.

Sooty3

But first you have to convert the IP to a ZIP code or coordinates and for that you need to use a service like ip2location. They do have a php sample under the developer tab, and some free services, but the full service requires payment.