my website always went down and when i change the php version it becomes alive.i have to do this all day to keep my website alive
When you say you change php version, do you change it to something else and change it back?
Also when you change php, you initiate an lsws restart so just try restarting litespeed to see if that solves the issue.
Check your inodes and make sure they arent full.
Clear php sessions for the php in question.
find /var/lib/lsphp/session/lsphp74/ -type f -name "sess_*" -delete >/dev/null 2>&1
Also check your logs for any errors.