On cPanel servers there’s a very easy way to install eAccelerator, IonCube, Zendopt, Suhosin and Source guardian without an Apache recompile with the PHP extension manager:
/scripts/phpextensionmgr
The usage is very straightforward. For instance to install IonCube you simply run from shell:
/scripts/phpextensionmgr install IonCubeLoader
And do not forget to restart Apache.