sending hierarchical data from javascript over flat POST request

Question

I have a page on which user can dinamically create some identical groups of inputs, fill it and send to server.

<input type="text" name="firstName"/>  
<input type="text" name="lastName"/>

What is a preferable way of sending this data to server?

Maybe there are some simple ways of emulating hierarhical data over POST request, avoiding XML structures? Different "name" attribute values ("firstName1", "firstname2")? Creating ID for each group or input? Relying on the order of name-value pairs in the POST request?

EDIT: of course i know about JSON. But just to use some minimal hierarchies i would like to follow the second answer: rely on the order of firstname-lastname in post request.

Answer 1

You could use JSON serialization instead of XML. On the browser side you could use one of the Javascript JSON libraries like this one and there's plenty of implementations for server side languages, which you can use for deserialization.

Answer 2

If the data pairs are ordered, you don’t need additional identifiers as the order already identifies the data pairs. So you could just use firstName and lastName for every data pair:

firstName=First%20Name%201&lastName=Last%02Name%201&firstName=First%20Name%202&lastName=Last%20Name%202&…

You server-side application then just combines each data pair.

But some languages/systems already do this when the data has a special format. In PHP you could use the arg[] syntax to automatically get an array of the data.