json_encode 在 arrayObject 与 array() 上的行为不同

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"
        }
      }

现在我已经重写了数组，使其成为这样的对象：

//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"
        }
      }
    }
  },

这使得它无法用作 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 ArrayAccess 接口的对象；使用公共属性。

要获得您想要的行为，您应该向其传递一个实际的数组，可以通过调用 ArrayObject::getArrayCopy() 来检索该数组（或者您可以将对象转换为数组）。

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

Answer 2

必须在不同级别转换包含 ArrayObject 的数据树，因此我编写了一段代码来在输出 json 之前处理和转换每个 ArrayObject，希望它有所帮助：
https://github.com/nfroidure/Rest4/blob/master /php/class.Json.php

Answer 3

使用 JsonSerialized 接口（PHP 5 >= 5.4.0、PHP 7) 你应该是安全的：

public function jsonSerialize()
{
    return $this->getArrayCopy();
}