Zip Code Range and Distance Calculation class

This is a PHP class to do various calculations with zip codes. Its primary purposes are to calculate the distance between two zip codes and to extract all the zip codes that are within a range of a given zip code. All calculations are based on lattitude and longitude coordinates stored in the database. Included is a class file, demonstration file, and the sql files required to create and populate the MySQL tables. ** UPDATE ** Added code to make the function which gets a range of zip codes execute ALOT faster. Went from 3.2 seconds to 0.42 seconds! Modification was submitted by Jeff Bearer