PHP将json $ _POST数据转换为数组

Question

I have json data like so:

 "[
  {
    \"sort\" : 0,
    \"wishlistid\" : 0,
    \"item\" : \"Test\",
    \"userid\" : 11
  }
]"

which I am getting from Swift via this Alamofire call:

 func saveWishList(_ cellHolder: Array<WishListClass>, completion: @escaping (_ result: Bool) -> Void)
{

    //Define Array of Dictionary

    var jsonArrayOfDictionaries = [[String: Any]]()

    //For each item in the cellHolder

    for i in 0..<cellHolder.count {

        //Define Dictionary for grading data

        var jsonDict = [String: Any]()

        jsonDict["userid"] = cellHolder[i].userid

        jsonDict["wishlistid"] = cellHolder[i].wishlistid

        jsonDict["item"] = cellHolder[i].item

        jsonDict["sort"] = cellHolder[i].sort

        jsonArrayOfDictionaries.append(jsonDict)

        jsonDict = [String: Any]()

    }

    let jsonData: Data? = try? JSONSerialization.data(withJSONObject: jsonArrayOfDictionaries, options: .prettyPrinted)

    let json = String(data: jsonData!, encoding: String.Encoding.utf8)

    let parameters: Parameters = [
        "wishList" : json!
    ]

    Alamofire.request(webservice + "?action=postuserwishlist", method: HTTPMethod.post, parameters: parameters, encoding: URLEncoding.httpBody, headers: [:]).responseJSON { response in

        if(response.error == nil)
        {
            if let result = response.result.value {

                let jsonData = result

                print(jsonData)

                completion(false)

            }
        }

    }
}

Now I am trying to retrieve the json posted into a php array....

So my question is how would I go about doing that in PHP? I am expecting an array in PHP with the key and value.