在PHP中使用XML到数组时出错

嗨，我试图将一个XML文件转换成php数组，除了这个节点之外，所有节点都变好了

<category name="Wheels and Tires">
<specification name="Front Tire Type">P245/40R18</specification>
<specification name="Front Wheel Diameter">18.0 x 8.0</specification>
<specification name="Rear Tire Type">P245/40R18</specification>
<specification name="Rear Wheel Diameter">18.0 x 8.0</specification>
</category>

---

转换为json然后返回没有意义：/n转换为json然后返回没有意义：/

$xml = curl_exec($ch); // $result now contains the response JSON or XML.
$xml_string = simplexml_load_string($xml);
$json = json_encode($xml_string);
$xml_parse = json_decode($json, TRUE);
return($xml_parse);

  array:2 [▼
    "@attributes" => array:1 [▶]
    "specification" => array:4 [▼
      0 => "P245/40R18"
      1 => "18.0 x 8.0"
      2 => "P245/40R18"
      3 => "18.0 x 8.0"
    ]
  ]