Unserializing complex POST data into objects

Suppose I have an HTML page with input data for the following relationship:

An User has the properties "given_name" and "family_name"

An User has N Phones (property "phones")

An User has 1 IdCard (property "idCard")

A Phone has the property "number"

An IdCard has the property "number"

Here's the HTML code:

<form method="POST">
    <p>
        <label>Given Name</label>
        <input type="text" name="User[given_name]" value="My"/>
    </p>

    <p>
        <label>Family Name</label>
        <input type="text" name="User[family_name]" value="Name"/>
    </p>

    <fieldset>
        <p>
            <label>Phone 1</label>
            <input type="text" name="User[Phone][][number]" value="7777-7777"/>
        </p>

        <p>
            <label>Phone 2</label>
            <input type="text" name="User[Phone][][number]" value="8888-8888"/>
        </p>

        <p>
            <label>Phone 3</label>
            <input type="text" name="User[Phone][][number]" value="9999-9999"/>
        </p>
    </fieldset>

    <p>
        <label>ID Card Number</label>
        <input type="text" name="User[IdCard][number]" value="0000.0000.0000"/>
    </p>

    <input type="submit"/>
</form>

How would you handle the POST data on the server-side to automatically unserialize it into instances of the respective objects?

Example of desired result (pseudocode):

user = unserialize(new User, request.POST)

assert user instanceof User
assert user.given_name == "My"
assert user.family_name == "Name"

assert user.phones instanceof Array
assert user.phones.length == 3

assert user.phones[0] instanceof Phone
assert user.phones[1] instanceof Phone
assert user.phones[2] instanceof Phone

assert user.phones[0].number == "7777-7777"
assert user.phones[1].number == "8888-8888"
assert user.phones[2].number == "9999-9999"

assert user.idCard instanceof IdCard
assert user.idCard.number == "0000.0000.0000"

I'm asking this because while some web frameworks focus on shiny examples of saving a todo message into a todo list (simple and almost unstructured data), real life makes me deal with complex forms with complex relationships, and apparently there's no common solution for the problem that I described.

I come from a PHP/Yii background. Am I missing something?