[FuzzyDunlop]

It's PHP 5.3's namespacing functionality, in a nutshell.

Symfony2 and Lithium are two frameworks I can currently think of that use them extensively. On the one hand, Symfony2 has a quite extreme implementation, and on the other, Lithium's is much more concise. The backslashes can be used to represent a hierarchy.

[snorkel]

Oh for the love of science, please let this be a bad dream ... is the parent object referred to as C:\ by any chance?

[robmorgan]

Zend Framework 2.0 is also a big user of PHP namespaces. It's in beta the moment.