vzool · April 17, 2017 13:00 · Apr 17, 2017
diff --git a/point-in-polygon.php b/point-in-polygon.php
@@ -0,0 +1,105 @@
+<?php
+/*
+Description: The point-in-polygon algorithm allows you to check if a point is
+inside a polygon or outside of it.
+Author: Michaël Niessen (2009)
+Website: http://AssemblySys.com
+ 
+If you find this script useful, you can show your
+appreciation by getting Michaël a cup of coffee ;)
+PayPal: [email protected]
+ 
+As long as this notice (including author name and details) is included and
+UNALTERED, this code is licensed under the GNU General Public License version 3:
+http://www.gnu.org/licenses/gpl.html
+*/
+
+class pointLocation {
+    var $pointOnVertex = true; // Check if the point sits exactly on one of the vertices?
+ 
+    function pointLocation() {
+    }
+
+    function pointInPolygon($point, $polygon, $pointOnVertex = true) {
+        $this->pointOnVertex = $pointOnVertex;
+
+        // Transform string coordinates into arrays with x and y values
+        $point = $this->pointStringToCoordinates($point);
+        $vertices = array(); 
+        foreach ($polygon as $vertex) {
+            $vertices[] = $this->pointStringToCoordinates($vertex); 
+        }
+
+        // Check if the point sits exactly on a vertex
+        if ($this->pointOnVertex == true and $this->pointOnVertex($point, $vertices) == true) {
+            return "vertex";
+        }
+
+        // Check if the point is inside the polygon or on the boundary
+        $intersections = 0; 
+        $vertices_count = count($vertices);
+
+        for ($i=1; $i < $vertices_count; $i++) {
+            $vertex1 = $vertices[$i-1]; 
+            $vertex2 = $vertices[$i];
+            if ($vertex1['y'] == $vertex2['y'] and $vertex1['y'] == $point['y'] and $point['x'] > min($vertex1['x'], $vertex2['x']) and $point['x'] < max($vertex1['x'], $vertex2['x'])) { // Check if point is on an horizontal polygon boundary
+                return "boundary";
+            }
+            if ($point['y'] > min($vertex1['y'], $vertex2['y']) and $point['y'] <= max($vertex1['y'], $vertex2['y']) and $point['x'] <= max($vertex1['x'], $vertex2['x']) and $vertex1['y'] != $vertex2['y']) { 
+                $xinters = ($point['y'] - $vertex1['y']) * ($vertex2['x'] - $vertex1['x']) / ($vertex2['y'] - $vertex1['y']) + $vertex1['x']; 
+                if ($xinters == $point['x']) { // Check if point is on the polygon boundary (other than horizontal)
+                    return "boundary";
+                }
+                if ($vertex1['x'] == $vertex2['x'] || $point['x'] <= $xinters) {
+                    $intersections++; 
+                }
+            } 
+        } 
+        // If the number of edges we passed through is odd, then it's in the polygon. 
+        if ($intersections % 2 != 0) {
+            return "inside";
+        } else {
+            return "outside";
+        }
+    }
+
+    function pointOnVertex($point, $vertices) {
+        foreach($vertices as $vertex) {
+            if ($point == $vertex) {
+                return true;
+            }
+        }
+
+    }
+
+    function pointStringToCoordinates($pointString) {
+        $coordinates = explode(" ", $pointString);
+        return array("x" => $coordinates[0], "y" => $coordinates[1]);
+    }
+
+}
+
+// Tests
+
+
+$pointLocation = new pointLocation();
+$points = array("50 70","70 40","-20 30","100 10","-10 -10","40 -20","110 -20");
+$polygon = array("-50 30","50 70","100 50","80 10","110 -10","110 -30","-20 -50","-30 -40","10 -10","-10 10","-30 -20","-50 30");
+// The last point's coordinates must be the same as the first one's, to "close the loop"
+foreach($points as $key => $point) {
+    echo "point " . ($key+1) . " ($point): " . $pointLocation->pointInPolygon($point, $polygon) . "<br>";
+}
+
+// Results 
+/*
+This will output:
+
+point 1 (50 70): vertex
+point 2 (70 40): inside
+point 3 (-20 30): inside
+point 4 (100 10): outside
+point 5 (-10 -10): outside
+point 6 (40 -20): inside
+point 7 (110 -20): boundary
+
+*/
No results found