Install pthreads for PHP in PLESK

I'm looking for a way to install pthreads in PLESK for PHP. I've searched a lot but can't find any tutorial or How-To for this. Is there anyone who can say me how I can install pthreads in PLESK?

krakjoe/pthreads

I need to do this because I'm getting an error message when I try to extend a class in PHP by Thread:

I've checked the installed modules in PLESK but there is no pthreads to enable...

Install pthreads for PHP in PLESK