swift - Sending struct through POST to php

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I have an iOS app that is written in Swift.

The app has a cart, with items of a struct called Order, which has a productName inside it.

When the order is finished, I am sending the data to a php file, so I can upload the data to my database.

The problem is, when I send the variable order containing the users wishes products with the Order struct, and then I get the variable on the PHP page like so:

$order = $_POST["order"];

When I echo $order; this is the response I get in the console of Xcode:

responseString = Optional("[MyAppName.Order]")

This is my Order struct:

struct Order: Codable {
   let productName: String
   let productQuantity: Int
   let productPrice: Int

   init(productName: String, productQuantity: Int, productPrice: Int) {
      self.productName = productName
      self.productQuantity = productQuantity
      self.productPrice = productPrice
   }

}

I guess I need to change the struct so it can be read in a PHP file. What can I do to change the data in the struct so it will be readable for a PHP file?