I know that but the PHP deserializer doesn’t know and gives me back an object instead of an array of one. If it’s two it detects an array.

But it's always a single object. If it has two parallel nodes at the document root, it isn't valid XML.

So an array of two results looks like this:

    <results>
      <result></result>
      <result></result>
    </results>

and PHP automatically treats results as a two-element array, but for the one-element array

    <results>
      <result></result>
    </results>

you just get a parse error?

Not a parse error but a single “result” object, not an array of length 1. With two elements it recognizes an array.

If you can parse

    <results>
      <result></result>
    </results>

and you end up with a single "result" object, you must have identified "results" as being an array of one element so that you could discard it. (You didn't get a single "results" object.)

That's not a problem in what XML is able to model, it's a problem with you throwing the information you got away and then pretending you didn't receive it.

On the other hand, if you meant that you get a single "results" object, then you're saying that your code is written to require invalid XML and fall down when valid XML is provided. Again, that sounds more like a problem with your code than with the modeling capabilities of XML. There's an argument to be made for accepting invalid input; rejecting valid input is ridiculous.

You do understand that php and quite a few other languages provide pre-built serialization and de-serialization from XML, right? The OP was talking about the out of box behaviour for those. Your answer seems to predicate on having written a custom deserializer.

My answer is predicated on the idea that you should be using a deserializer that doesn't rely on receiving invalid input, regardless of whether that deserializer comes from a standard library.