class - What are some useful ways to utilize classes in PHP? -

I have learned how classes are used in PHP and so far I have found only one useful application for them. I have created a user class in my web application to prioritize the various tasks related to such users, such as avatar output, ect show the number of messages.

In addition to this example, what are some other useful ways to use classes, a practical understanding?

I use database squares all the time