KDevelop 4 is still in beta, but this guide will help get it running.
Arch Testing has a build of KDevelop4, but to get the newest features install it from an SVN build. You can use the repositories below for nightly builds.
These repositories provides both kdevelop-svn and kdevplatform packages, but not the kdevelop-pg package that is required to build additional plugins.
Building Additional Plugins
First: Install Dependency
AUR has the kdevelop-pg-qt-svn package that is required to build additional plugins. Plugins will not compile if this package is not installed beforehand.
The PHP plugin provides autocompletion and other PHP-specific features.
Checkout the PHP plugin from SVN
Change into the new directory (php) and run CMake, taking care to specify the installation directory.
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr .
Now make and install the package. The 'make install' command must be run as root.
make && make install
Restart KDevelop 4 and you should now have improved PHP support, including autocomplete for both the PHP functions as well as for your project's functions and classes.
Other plugins should compile the same way as the ones above. When doing the svn checkout simply change the last directory name to the plugin directory from KDE's websvn browser.
For example, to install the Python plugin you can use the instructions for PHP, but change the svn checkout line from
svn checkout svn://anonsvn.kde.org/home/kde/trunk/playground/devtools/kdevelop4-extra-plugins/python
If you have successfully installed one of these additional plugins please add a relevant section to this wiki page with the exact instructions.
Note: As of June 17 2009, do not install the php-docs plugin because it causes the php plugin to stop working.