Google Map: is a lat/lng within a polygon?

Question

Given a pair of lat/lng values, how do I determine if the pair is within a polygon? I need to do this in PHP. I see that Google Maps API has a containsLocation

Answer 1

One way to find if a point is in a polygon is to count how many times a line drawn from the point (in any direction) intersects with the polygon boundary. If they intersect an even number of times, then the point is outside.

I have implemented the C code from this Point in Polygon article in php and used the polygon below to illustrate.

=$y 
 ||  $polyY[$j]<$y && $polyY[$i]>=$y) {
    if ($polyX[$i]+($y-$polyY[$i])/($polyY[$j]-$polyY[$i])*($polyX[$j]-$polyX[$i])<$x)    {
    $oddNodes=!$oddNodes; }}
   $j=$i; }

  return $oddNodes; }


 if (pointInPolygon($polySides,$polyX,$polyY,$x,$y)){
  echo "Is in polygon!";
}
else echo "Is not in polygon";
?>