在CentOS 6.6中从PHP 5.3.3升级到PHP 5.5是否安全？

I need to install a plugin on my website which requires PHP >= 5.5. Right now i'm running PHP 5.3.3 on CentOS 6.6.

1. Is it safe tou upgrade PHP or there is a a tangible risk that some applications won't work after upgrade?
2. Is there a way to "rollback" the upgrade? So that i upgrade, i check that everything works and, if not, i downgrade.

Thanks!

Yes, there is a chance that some applications won't work. I upgraded from 5.3 to 5.4 on a system and found that a bug appeared in production code. It wasn't anything that couldn't be fixed. Of course, there have been other times where an upgrade worked flawlessly.

If you install 5.5 on the system without disturbing the 5.3 installation then it should be possible to rollback to 5.3 if needed. Just save the server configuration for 5.3 before pointing it to 5.5.