apt-cache policy php5-dev
How can i get the latest stable version (5.35) using apt, i understand i need to add a repository to my sources but how do i find one?
I just noticed you use Ubuntu. Those repositories are designed for Debian but many users report success using them with Ubuntu.
Ubuntu as debian stores all packages into a pool, so you can just search for php in the ubuntu packages, right now for natty you have 5.3.3 (http://packages.ubuntu.com/natty/php5-common)
Another way would be to build your own deb package, you can start doing so by downloading the packages you see on the natty release and play with