I think this cannot be done do to the fact the PHP is a stateless language. But I will ask anyway...
I've created a home-grown MVC framework. The classes are all namespaced. On initial load I instantiate my custom Autoload class. A method of this class scans registered class directories (stored in the application config) and creates an array of fully qualified class names to paths. The array is stored as a protected member of this class. This member array is used by the spl_autoload() implementation. The Autoloader object is cached and reused on each http request.
This is fine and well. However, it irks me that every time an http request comes in to the domain my bootstrap routine has to register the autoload method to the __autoload stack. I would love to register it once and leave it alone.