Mark, thank you for your prompt answer. No, I didn't see any such message. As a matter of fact, I got my website back after emptying all page caches. I'm not a programmer so I have no idea why it worked, but since the error was issuing from two php files somehow related with it, I decided to give it a go. I was fortunate enough to be able to go to my dashboard, for otherwise I wouldn't have known how to do it. But that somehow fixed it. I have Update WF automatically unchecked because my server doesn't allow such a thing and I don't see any messages about LiteSpeed web server.
Please take this into account to better deal with this issue if it ever presents again.
Thank you,
Xondra.