从命名空间中的变量获取类

Question

I'm trying to update my project with namespaces.
Before using namespaces I could easily call a class via a variable like so:

<?php
    $className = "Item";
    $myClass = new $className();
?>

Now, when using namespaces (with use) I'd expect this to work:
(not working allways meens: 'Can't find class' or smth like this)

<?php
    namespace myProject
    use myProject\Models

    $className = "Item";
    $myClass = new $className();   // this class has the namespace myProject\Models
    // this doesn't work! (can't find class)
    $myClass = new Models\$className();
    // nope, doesn't work either
    $myClass = new myProject\Models\$className();
    // nope
?>

but calling the same class directly - without a variable - IS working

$myClass = new Item();

What I have to do, to make it work is:

<?php
    namespace myProject;
    use myProject\Models;   // unnessecary now

    $className = "\\" . __NAMESPACE__ . "\\Models\\" . "Item";
    $myClass = new $className(); 
?>

My question now is:
If I want to call a class via a variable, do I really have to include the whole namespace as a fully qualified name?

EDIT: I found myself an answer here: Dynamic namespaced class with alias
I'll keep that question anyway, because I could not find the right answer in first place.