Original question Check if a latitude and longitude is within a circle
I would like to know how this can be achieved using PHP. I have an array of latitudes and longitudes and would like to test them against another array of latitudes/longitudes to give a true/false scenario
I've prepared the sample code snippet for you. It's working well for me. Feel free to adapt with your own logic.
$lat1 = "10.5900627";
$lon1 = "77.1933317";
$lat2 = "10.6068507";
$lon2 = "77.117246";
function distance($lat1, $lon1, $lat2, $lon2, $unit)
{
if (($lat1 == $lat2) && ($lon1 == $lon2)) {
return 0;
}
else {
$theta = $lon1 - $lon2;
$dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
$dist = acos($dist);
$dist = rad2deg($dist);
$miles = $dist * 60 * 1.1515;
$unit = strtoupper($unit);
if ($unit == "K") {
return ($miles * 1.609344);
} else if ($unit == "N") {
return ($miles * 0.8684);
} else {
return $miles;
}
}
}
if(distance($lat1, $lon1, $lat2, $lon2, "K") < 10)
{
echo "True";
}
else
{
echo "False";
}
If the result of 'K' is less than 10Km, then you will get the result as "True". Otherwise 'False' will return as result.
I would do it this way, first I'll need to compute the distance between two points (this is a method close to the one of Google Maps: https://stackoverflow.com/a/53069194/7071905) :
function computeDistance($lat1, $lng1, $lat2, $lng2, $radius)
{
static $x = M_PI / 180;
$lat1 *= $x; $lng1 *= $x;
$lat2 *= $x; $lng2 *= $x;
$distance = 2 * asin(sqrt(pow(sin(($lat1 - $lat2) / 2), 2) + cos($lat1) * cos($lat2) * pow(sin(($lng1 - $lng2) / 2), 2)));
return $distance * $radius;
}
Then I'll need a simple function with the base point (the center) to return true when the distance is below 10 kilometers ($KM) :
function isWithinCircle($lat, $lng, $KM = 10): bool
{
$baseLat = 0;
$baseLng = 0;
$radius = 6378137;
return computeDistance($baseLat, $baseLng, $lat, $lng, $radius) <= $KM;
}