PHP started at a time when web development was not considered "serious programming". I mean, people switched to it from building GUI or console apps on C/C++ and Perl. It was fast, efficient, had convenient hashtables and defaults in place, and it was better than writing simple HTML files, but it was still considered "scripting". Nowadays, web apps are a lot more complicated, but web development is still messy: as HTML always stands in the way, it's still hard to abstract the whole web development process without restricting yourself to a specific mode of development and its limitations.