在PHP中将大对象数组声明为javascript参数

Question

I need to pass a PHP array to a javascript function where the array has the form

var Waypoints = [{"Geometry":{"Latitude":52.34,"Longitude":55.35}},{"Geometry":{"Latitude":55.34,"Longitude":56.35}}]

Here is a code snippet:

class Geometry
{
  public $Latitude;
  public $Longitude;
}
class WayPoint
{
  public $Geometry;
}
$Geometry = new Geometry();

$wp = new WayPoint();
$wp->Geometry->Latitude = 52.34;
$wp->Geometry->Longitude = 55.35;

$wp2 = new WayPoint();
$wp2->Geometry->Latitude = 55.34;
$wp2->Geometry->Longitude = 56.35;

$php_data = [$wp,$wp2 ];
echo json_encode($php_data);

which produces this:

[{"Geometry":{"Latitude":52.34,"Longitude":55.35}},{"Geometry":{"Latitude":55.34,"Longitude":56.35}}]

This is the correct array structure, however I am asking two questions:

1. Is this the best way of declaring the object classes with regarding to filling the array with a very large number of co-ordinates, and
2. Why is PHP giving a warning for the code on lines, 13 and 16 regarding empty values, i.e.

Warning: Creating default object from empty value in for $wp->Geometry->Latitude = 52.34; and $wp2->Geometry->Latitude = 55.34;

From what I can discern from the documentation, this is the correct way of declaring an object, and why is it just the first variable is being flagged?

Answer 1

The error is because you dont assign the Geometry property of the Waypoint objects.

It still works because php will create a default object (called a stdClass) when you assign a property to a non existent variable.

There is a much simpler solution - json_encode will take an asociative array as input:

echo json_encode(
    [
        [
            'Geometry'=>
                [
                    'Latitude'  =>  52.34,
                    'Longtitude'=>  55.35,
                ]
        ],
        [
            'Geometry'=>
                [
                    'Latitude'  =>  52.65,
                    'Longtitude'=>  56.35,
                ]
        ],
    ]
);

Obviously you can build this array in a loop.

If you do want to use named classes, for other reasons, then the correct code would be:

class Geometry
{
  public $Latitude;
  public $Longitude;
}
class WayPoint
{
  public $Geometry;
}

$data=[];


$wp = new WayPoint();
$gm = new Geometry();
$gm->Latitude = 52.34;
$gm->Longitude = 55.35;

$wp->Geometry = $gm;

$data[]=$wp;


echo json_encode($data);