PHP serialize data case

Hi
Problem is, what to do, if users data is unknown. I mean, different fields and difefrent amount of them are needed to log some events.
I can use serialization of data, using one column as comments. May I will use it, when i dont know ,either data will be important or not for future purposes, and variable (field) amount is not clear for different users.

I heard, that some persons are using two fields in tables: ID and DATA



and data contains all serialized variables- fields. Example in PHP can be found

PHO serialize example

I am not sure am i right. I am not sure about performanve of such method

Can somebody comment?

Best regards

Do you have any questions (besides, "comments please?") about serializing your data? The subject is very broad and it wouldn't be very good to go off on a tangential discussion completely unrelated to what you're wanting help with (are you wanting help?).