PHP, unless it has changed radically since 2009, is pretty horrendous as a language, there are, IMO, far, far better choices on the dynamic side of the fence (e.g. Python, Ruby, Groovy).

It does get the job done, as you say, but being able to patch a running application with oh-just-this-one-quick-fix is not necessarily a good thing as it can encourage one to fall into the opposite of programmer best practices (was the case for me, I completely understand why DHH of Rails fame said [tongue in cheek], "PHP is the devil!")

Scala, on the other hand, basically changes your brain chemistry. Compared to where I was in 2009, floundering in dynamic language hacking with PHP, and later, Groovy, Scala has completely changed my approach to programming.

Obviously the rich Scala ecosystem has something to do with that, but the language itself really just helps guide you to "correct" solutions (FP constructs in particular). At this point I cannot imagine going back to a server-side dynamic language.