用PHP计算坐标到多边形的距离

计算一个点到多边形的距离可以使用以下步骤：

1. 定义多边形顶点，使用数组表示多边形的每个顶点，例如：

   $vertices = array(
       array('x' => 0, 'y' => 0),
       array('x' => 0, 'y' => 5),
       array('x' => 5, 'y' => 5),
       array('x' => 5, 'y' => 0),
   );

2. 定义目标点坐标，例如：

   $target = array('x' => 2, 'y' => 2);

3. 计算目标点到多边形每条边的距离，找到最短的距离，例如：

   $minDistance = null;
   foreach ($vertices as $i => $v1) {
       $v2 = $vertices[($i + 1) % count($vertices)];
       $distance = pointToLineDistance($target['x'], $target['y'], $v1['x'], $v1['y'], $v2['x'], $v2['y']);
       if ($minDistance === null || $distance < $minDistance) {
           $minDistance = $distance;
       }
   }

4. 使用以下函数计算点到直线的距离：

   function pointToLineDistance($x, $y, $x1, $y1, $x2, $y2) {
       $A = $x - $x1;
       $B = $y - $y1;
       $C = $x2 - $x1;
       $D = $y2 - $y1;

       $dot = $A * $C + $B * $D;
       $len_sq = $C * $C + $D * $D;
       $param = -1;
       if ($len_sq != 0) {
           $param = $dot / $len_sq;
       }

       $xx = 0;
       $yy = 0;
       if ($param < 0) {
           $xx = $x1;
           $yy = $y1;
       } elseif ($param > 1) {
           $xx = $x2;
           $yy = $y2;
       } else {
           $xx = $x1 + $param * $C;
           $yy = $y1 + $param * $D;
       }

       $dx = $x - $xx;
       $dy = $y - $yy;
       return sqrt($dx * $dx + $dy * $dy);
   }

完整代码如下：

function pointToLineDistance($x, $y, $x1, $y1, $x2, $y2) {
    $A = $x - $x1;
    $B = $y - $y1;
    $C = $x2 - $x1;
    $D = $y2 - $y1;

    $dot = $A * $C + $B * $D;
    $len_sq = $C * $C + $D * $D;
    $param = -1;
    if ($len_sq != 0) {
        $param = $dot / $len_sq;
    }

    $xx = 0;
    $yy = 0;
    if ($param < 0) {
        $xx = $x1;
        $yy = $y1;
    } elseif ($param > 1) {
        $xx = $x2;
        $yy = $y2;
    } else {
        $xx = $x1 + $param * $C;
        $yy = $y1 + $param * $D;
    }

    $dx = $x - $xx;
    $dy = $y - $yy;
    return sqrt($dx * $dx + $dy * $dy);
}

function pointToPolygonDistance($target, $vertices) {
    $minDistance = null;
    foreach ($vertices as $i => $v1) {
        $v2 = $vertices[($i + 1) % count($vertices)];
        $distance = pointToLineDistance($target['x'], $target['y'], $v1['x'], $v1['y'], $v2['x'], $v2['y']);
        if ($minDistance === null || $distance < $minDistance) {
            $minDistance = $distance;
        }
    }
    return $minDistance;
}

$vertices = array(
    array('x' => 0, 'y' => 0),
    array('x' => 0, 'y' => 5),
    array('x' => 5, 'y' => 5),
    array('x' => 5, 'y' => 0),
);
$target = array('x' => 2, 'y' => 2);

$distance = pointToPolygonDistance($target, $vertices);
echo "Distance is: " . $distance;