As someone said, there are many paradigms. I like everything done by pragmatic programmer, but there is a book Seven Languages in Seven Weeks that gives a good survey of what's out there.

Php is a dynamic language for sure. And you can pick it up quickly and get some work done, even if you don't have any idea about "software development." Php gets beat up a lot because you can get some work done using just the core of the language. You can also put run it right in your html. Of course, I could use C# inline in an ASP.Net page in the same way if I wanted (you can use ASP.net just like classic ASP, if you really want to). I think it's just less common to see "hacks on top of hacks" code in languages that aren't free because hobbyist will use the free stuff instead. To write a serious php aplication, you would use a framework--maybe Zend or Symphony. Or you could also use one of the many microframeworks--laravel and limonade are among my favorites. Or you could start with an extensible platform like Wordpress, Drupal, OsCommerce, Moodle, etc. Most of the php projects I have worked on are integration projects...like merging functionality from moodle into a drupal site, or merging a wordpress blog into an OsCommerce store, or something like that. Evaluating Php by reading wordpress plugins writtne by hobbyist is a lot like evaluating .Net by reading consile apps written by students, in my opinion. Look into the frameworks that are available and the code that is in the platforms like wordpress to see how professional programmers use php.