PHP 根据两坐标绘制延长线

function calcPoiGroupsExtendPoi($startPoi, $endPoi, $d)
    {
        $r = sqrt(pow($startPoi['x'] - $endPoi['x'], 2) + pow($startPoi['y'] - $endPoi['y'], 2));

        return [
            's' => [
                'x' => (-$d * ($endPoi['x'] - $startPoi['x'])) / $r + $startPoi['x'],
                'y' => (-$d * ($endPoi['y'] - $startPoi['y'])) / $r + $startPoi['y'],
            ],
            'e' => [
                'x' => ($d * ($endPoi['x'] - $startPoi['x'])) / $r + $startPoi['x'],
                'y' => ($d * ($endPoi['y'] - $startPoi['y'])) / $r + $startPoi['y'],
            ],
        ];
    }
    ```