Radians error message with Lat / Lon calculation

Question

I'm creating a website with an events calendar where users search by location (lon/lat) and I found this online which has a calculation but I keep getting the error:

Fatal error: Call to undefined function RADIANS() in ...

Why I may be getting this?

My calculation is:

$calc = 6378.137 * acos( Cos( RADIANS(lat) ) * Cos( RADIANS('$yourlat') ) * Cos( RADIANS('$yourlon') - RADIANS(lon) ) + Sin( RADIANS(lat) ) * Sin( RADIANS('$yourat')));

$get_events_sql = "SELECT * FROM events WHERE '$calc' <= 10";

Answer 1

RADIANS is a MySQL function, but you're trying to call it in php. If you want to convert degrees to radians in PHP, you can define this function.

    function RADIANS($degrees)
    {
         return 0.0174532925 * $degrees;
    }

Or, you can just multiply by that constant. (360 degrees is 2π radians)