How to Calculate the Distance Between Two Zip Codes Using PHP?

Calculating Distance Between Zip Codes in PHP

Users often need to determine the distance between two locations. This becomes more complex when dealing with zip codes, as they represent geographic areas with varying boundaries. However, by utilizing latitude and longitude data, it's possible to calculate these distances accurately.

To address this need, a user sought assistance in calculating the distance between two zip codes using PHP. The database contained the following fields: ZIP, LATITUDE, LONGITUDE, CITY, STATE, COUNTY, and ZIP_CLASS.

The solution involves utilizing the spherical law of cosines, which calculates the great-circle distance between two points on a sphere. This formula considers the Earth's radius and the differences in latitude and longitude between the two points.

The provided code showcases a function called calc_distance that receives two points as arguments, each representing a zip code with associated latitude and longitude. The function calculates the distance between these two points using the following steps:

1. Converts latitude and longitude values to radians for accurate calculations.
2. Calculates the difference in latitude and longitude between the two points in radians.
3. Uses the spherical law of cosines to compute the distance based on the Earth's radius.
4. Returns the calculated distance using the same units as the input radii (typically miles or kilometers).

By incorporating this function into a web application, users can easily calculate and display the distance between two zip codes they input on the website.

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