What are common pitfalls to avoid when working with geographic coordinates in PHP to ensure accurate distance calculations?

Common pitfalls to avoid when working with geographic coordinates in PHP include not converting coordinates to radians before performing calculations, using incorrect formulas for distance calculations, and not considering the curvature of the Earth. To ensure accurate distance calculations, always convert coordinates to radians, use the Haversine formula for distance calculations, and take into account the Earth's radius.

function calculateDistance($lat1, $lon1, $lat2, $lon2) {
    $lat1 = deg2rad($lat1);
    $lon1 = deg2rad($lon1);
    $lat2 = deg2rad($lat2);
    $lon2 = deg2rad($lon2);
    
    $earthRadius = 6371; // Earth's radius in kilometers
    
    $deltaLat = $lat2 - $lat1;
    $deltaLon = $lon2 - $lon1;
    
    $a = sin($deltaLat/2) * sin($deltaLat/2) + cos($lat1) * cos($lat2) * sin($deltaLon/2) * sin($deltaLon/2);
    $c = 2 * atan2(sqrt($a), sqrt(1-$a));
    
    $distance = $earthRadius * $c;
    
    return $distance;
}