I recently read that php applications can be deployed on Google App Engine using Quercus.
Is it possible to deploy cakephp applications too? Also, from the developer
Update 10/03/13
GAE now supports PHP on an experimental basis. Check out the documentation here Landing page details other details
Original answer:
Officially GAE supports Java, Python and Go! But as detailed in post PHP can be made to work on GAE.
Though you must understand that PHP is being interpreted into Java bytecode and being run with certain limitations, as specially mentioned in point 4 in notes section.
The blog details everything you possibly need to know in great detail.