OOP is a must if you are working on large projects

From what i see in my country (Romania), OOP knowledge and experience has become a must in all of the professional companies over here (including most of the startups).

I've got my new job 9 months ago, and MVC knowledge was also required (experience not).

We still get "plain php" tasks (meaning writing stuff with global functions), but always use a MVC framework, or even if it is not necessary, we still follow the MVC pattern.

Using the MVC pattern helps both you and the designers, as everyone who does the styling and building the html, isn't forced to learn everything about PHP and isn't forced to read a lot of code just to change the appearance of a form. And you are mostly free of the risks of something being screwed up by the designer staff.

I believe, that any projects that need at least form processing, or rudimentary user related functions (login, user data, etc.) need to be done with classes. Should the client come up with some twisted idea, it will be easier to change stuff, as you plug new functions in and go.

Since i use OOP and the MVC pattern i need less and less maintenance time.

Exactly, OOP is the key to make your code more organized and easier to maintain.