PHP 5 and namespaces
The developers of the PHP Namespaces in violation of the PHP license :( But lets not go into the license violation. There was a massive thread on the PHP internals mailing list about namespaces and who liked what ascii character to specify namespaces. Rasmus even went as far as to say that : and :: are not going to be valid.
Ideally you can import say PEAR's Date class into the PEAR namespace while using Derick's Date class in the the PHP namespace. Not sure which implementation they are going to implement but apparenlty there are four including one from Dimitry from Zend Technologies who originally wrote the Turck MMCache software.