判断一个经纬度是否在一个围栏内

public function is_point_in_polygon($point, $pts) {
        $N = count($pts);
        $boundOrVertex = true; //如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true
        $intersectCount = 0;//cross points count of x
        $precision = 2e-10; //浮点类型计算时候与0比较时候的容差

        $p = $point; //测试点

        $p1 = $pts[0];//left vertex
        for ($i = 1; $i <= $N; ++$i) {//check all rays

            if ($p['lng'] == $p1['lng'] && $p['lat'] == $p1['lat']) {
                return $boundOrVertex;//p is an vertex
            }

            $p2 = $pts[$i % $N];//right vertex
            if ($p['lat'] < min($p1['lat'], $p2['lat']) || $p['lat'] > max($p1['lat'], $p2['lat'])) {//ray is outside of our interests
                $p1 = $p2;
                continue;//next ray left point
            }

            if ($p['lat'] > min($p1['lat'], $p2['lat']) && $p['lat'] < max($p1['lat'], $p2['lat'])) {//ray is crossing over by the algorithm (common part of)
                if($p['lng'] <= max($p1['lng'], $p2['lng'])){//x is before of ray
                    if ($p1['lat'] == $p2['lat'] && $p['lng'] >= min($p1['lng'], $p2['lng'])) {//overlies on a horizontal ray
                        return $boundOrVertex;
                    }

                    if ($p1['lng'] == $p2['lng']) {//ray is vertical
                        if ($p1['lng'] == $p['lng']) {//overlies on a vertical ray
                            return $boundOrVertex;
                        } else {//before ray
                            ++$intersectCount;
                        }
                    } else {//cross point on the left side
                        $xinters = ($p['lat'] - $p1['lat']) * ($p2['lng'] - $p1['lng']) / ($p2['lat'] - $p1['lat']) + $p1['lng'];//cross point of lng
                        if (abs($p['lng'] - $xinters) < $precision) {//overlies on a ray
                            return $boundOrVertex;
                        }

                        if ($p['lng'] < $xinters) {//before ray
                            ++$intersectCount;
                        }
                    }
                }
            } else {//special case when ray is crossing through the vertex
                if ($p['lat'] == $p2['lat'] && $p['lng'] <= $p2['lng']) {//p crossing over p2
                    $p3 = $pts[($i+1) % $N]; //next vertex
                    if ($p['lat'] >= min($p1['lat'], $p3['lat']) && $p['lat'] <= max($p1['lat'], $p3['lat'])) { //p.lat lies between p1.lat & p3.lat
                        ++$intersectCount;
                    } else {
                        $intersectCount += 2;
                    }
                }
            }
            $p1 = $p2;//next ray left point
        }

        if ($intersectCount % 2 == 0) {//偶数在多边形外
            return false;
        } else { //奇数在多边形内
            return true;
        }
    }

 

$point = ['lng'=>116.394299,'lat'=>40.011674];

$pts = [
    ['lng'=>115.934109, 'lat'=>40.124809],
    ['lng'=>116.554836, 'lat'=>40.177293],
    ['lng'=>116.620754, 'lat'=>39.783734],
    ['lng'=>116.054958, 'lat'=>39.809057]
];