如何在Ubuntu上安装PHP pthreads扩展?

I'd like to install the 'pthreads' PHP extension on Ubuntu. I'm using Ubuntu 12.04.1 LTS. And I can upgrade if needed. I really don't want to compile anything from source. For example recompile PHP from source sounds like a horrible idea to me.I'd like to install the 'pthreads' PHP extensio