This is a straw man. Citing 2 popular web sites and 1 application doesn't mean PHP is a well designed language. You could just as well have picked 2 other web sites written in Java to argue that PHP is rubbish.

I wouldn't even call it influential, unless language developers have been inspired about how not to design a language. Popular, yes, but not influential. I don't see anything from it being incorporated into other languages. It generally seems to have been playing catch up in terms of features, in a similar way to javascript (where there it's less about catch-up and more about breaking out of the browser & supporting OO).