
Re: PHP editor with in-place code navigation?
In
PHPEdit (Full featured PHP IDE and Editor with free trial), you can use Ctrl+F12 or contextual menu to jump to declaration as visible on this screenshot:
or

.
This feature is available for all function, methods, classes, interfaces, including support for PHP 5.3's namespaces.
In supported frameworks like Prado and Symfony you can jump between controllers and view.