我试图对一个对象进行json_编码，但我希望外部 Package 器是一个数组，而不是一个对象。
我试过了 json_encode($myObject, JSON_OBJECT_AS_ARRAY) 但我的最终结果总是

{
  "SALDOC": [
    {
      "SERIES": null,
      "TRDR": null,
      "PAYMENT": "2",
      "SHIPMENT": "",
      "TRNDATE": "2019-03-11 07:57:38",
      "REMARKS": null,
      "DISC1VAL": "0.0000",
      "SALESMAN": null,
      "SHIPKIND": null,
      "CCCCLCOURIERWEIGHT": "1.0000"
    }
  ],
  "ITELINES": [
    {
      "LINENUM": null,
      "VAT": null,
      "MTRUNIT4": null,
      "MTRCATEGORY": null,
      "MTRL": null,
      "QTY1": "1.0000",
      "PRICE": "15.0000"
    }
  ],
  "MTRDOC": [
    {
      "SHPZIP": "test",
      "SHPCITY": "teset",
      "SHIPPINGADDR": "test",
      "SHPDISTRICT": 100
    }
  ],
  "SRVLINES": [],
  "EXPANAL": []
}

如何使外 Package 成为数组[]而不是对象{}？