php/mysql zip code proximity search

Question

I\'m just looking for suggestions on the best way to do this...

I need to create a search function that searches for \"users\" within a 50 mile radius of a zip code

Answer 1

I'd consider reducing the number of candidates with a bounding square first, then worrying about the radius as a second step. You start off with the coordinates of the zipcode, then calculate the long/lat of 50 miles in all 4 directions, then select only candidates within that box using simple greater/less than criteria. If your user base is well spread out this reduces your candidate set considerably, then you only have to do vector distance math to eliminate the "corners".