php - json_encode 在 arrayObject 和 array() 上表现不同

Question

我在 php 中有一个函数:

//simple method with array()
$sensors = array();
$query = "select id, x(transform(wkb_geometry,". $epsg . ")) as lon, y(transform(wkb_geometry,". $epsg . ")) as lat from mytable;";
$result = pg_query($query) or die('Query failed: ' . pg_last_error());
while ($row = pg_fetch_assoc($result)) {
    //var_dump($row);
    $mySensor = new sensor($row['id'],$row['lat'],$row['lon']);
    $sensors[] = $mySensor->geoJSON();
}

echo json_encode($sensors);

输出:

"features": [{
    "type": "Feature",
    "id": 1579028,
    "x": 4.85310557823,
    "y": 52.7205622103,
    "geometry": {
      "type": "Point",
      "coordinates": [4.85310557823, 52.7205622103],
      "crs": {
        "type": "OGC",
        "properties": {
          "urn": "urn:ogc:def:crs:OGC:1.3:CRS84"
        }
      }

现在我重写了数组，变成了这样的对象:

//advanced method with arrayObject:
class sensors extends ArrayObject {
    function __construct($epsg){
        $query = "select id, x(transform(wkb_geometry,". $epsg . ")) as lon, y(transform(wkb_geometry,". $epsg . ")) as lat from mytable;";
        $result = pg_query($query) or die('Query failed: ' . pg_last_error());
        while ($row = pg_fetch_assoc($result)) {
            //var_dump($row);
            $mySensor = new sensor($row['id'],$row['lat'],$row['lon']);
                $this[] = $mySensor->geoJSON();
            }
        }
    }
}
$newsensors = new sensors($epsg);
echo echo json_encode($newsensors);

但这会将输出更改为:

"features": {
  "0": {
    "type": "Feature",
    "id": 1579028,
    "x": 4.85310557823,
    "y": 52.7205622103,
    "geometry": {
      "type": "Point",
      "coordinates": [4.85310557823, 52.7205622103],
      "crs": {
        "type": "OGC",
        "properties": {
          "urn": "urn:ogc:def:crs:OGC:1.3:CRS84"
        }
      }
    }
  },

这使得它不能用作 OpenLayers 的 geoJSON。为什么 json_encode 函数会这样？我可以关闭索引号的设置吗？这可能是一个小错误吗？

Answer 1

json_encode 将对任何对象显示相同的行为，即使是像 ArrayObject 那样实现了 ArrayAccess 接口(interface)的对象；使用公共(public)属性。

要获得您想要的行为，您应该将一个实际数组传递给它，该数组可以通过调用 ArrayObject::getArrayCopy() 检索(或者您可以将对象转换为数组)。

echo json_encode($newsensors->getArrayCopy());