XCache is a combo of
1. OPCode cache (to speed up PHP code execution by caching bytecode)
2. Variable cache ( to realise so-called object caching (KEY-VALUE storage) similar to redis or memcached, but you dont need any external software, thus its faster)
Unfortunately XCache supports only up to and including PHP 5.6 , which is EOL'd long time ago.
So you'll better look for other solutions