As PHP performs badly, another approach is required

Extensions are hard to write

You can only write extensions in C

Who here has tried to write an extension, or considered it?

There are plenty of extensions, so plenty of examples

There are also extensions in C++ (SDO, SCA, Colorer...)

Extensions are hard to use, as you need to recompile PHP

Shared objects, even closed source exist (Zend, ioncube)

Documentation is hard to find