How can we improve WHMCS?

Add a check for sane configuration of the PHP config values 'session.gc_probability' and 'session.gc_divisor'.

If either of these values are 0 no garbage collection it performed on stale session storage.
Which can result in saved stale sessions taking up GB of disk space and increasing page load times as PHP searches for a session ID match.

# PHP defaults
session.gc_probability = 1
session.gc_divisor = 100
- This runs session garbage collection during 1% of requests

# cPanel Production Recommendation
session.gc_probability = 1
session.gc_divisor = 1000
- This runs session garbage collection during 0.1% of requests, Recommended for high volume production servers.

#Reference
https://whmcs.community/topic/293996-tblsessions-huge-size
https://docs.whmcs.com/Sessions#Sessions_are_not_being_removed_automatically