Are you arguing that PHP is the quickest way to get started in the case where you already know PHP but not any other language, i.e. writing a program in PHP com

Are you arguing that PHP is the quickest way to get started in the case where you already know PHP but not any other language, i.e. writing a program in PHP compared to learning another language from scratch and then writing the same program in that language? That's probably true. But if PHP is the only language you know, it might still be worthwhile to learn another one, when you have some time to spare. And "most mature"? Other web frameworks are plenty mature. Django, Rails and Spring MVC are all roughly 15 years old.