If you are already using PHP and want to focus your learning on MVC and the use of frameworks (and not on another language/platform), I’d suggest using Laravel or another PHP-based framework.
I myself find it challenging learning a new concept on top of a new language and/or platform with a new tool, etc. When I learn a new programming language, I do so by porting an application I have already written into the new language. I learned PHP after porting a shopping cart I wrote in ASP 15+ years ago (and will do the same with Laravel myself plus all these other new (to me) languages that I am learning). Doing so allowed me to focus on just learning PHP rather without having to worry about the design, logic in the application, database design, etc.
Just about any platform/language will get the job done (and I plan on having a shopping cart in multiple languages/platforms on my portfolio). But if the goal is learning, I feel it’s better if you can isolate new programming concepts inside of an environment you’re already comfortable with. Otherwise, when things go wrong, it’s that much more frustrating to learn and/or troubleshoot when things go wrong because you don’t know and/or have enough experience to know where to even start looking for the source of your problems.