So the package manager version is 4.5.1, which is more than a few eyars old. Since I'm running Mint/Mate what is the most proper way to get the latest Kdevelop, especiall kdevelop-php? Are there any .deb files or PPAs available?

Depending on which version Mint 16 corresponds to, you could try the Kubuntu Lime PPAs.
I'm not aware of any other PPAs which would contain the latest version of any KDE applications (including KDevelop).