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If you favor Windows, C#, ASP.NET (MVC and Web Forms), WPF (though there is some stuff I haven't tried yet... maybe it'd be called WinRT), Windows Forms. Pretty much anything .Net Framework. All of this is done in Visual Studio.
If you favor Mac OS, Ruby on Rails, Objective-C, Cocoa.
For web stuff, jQuery, Ajax, Web Services, Cloud Computing (e.g., Azure, Amazon Cloud).
Is PHP a viable language though, meaning is it actually used for real stuff
It seems like a server-side scripting language from what I've seen of it (not much). And that's not a compliment. Basically, it has a low learning curve, but it doesn't seem designed for more complex software. I hear it's the most common language used for web work, but then most websites are complete garbage, so that makes sense.
Some notable exception to the rule that PHP is used for simple stuff are MediaWiki, which is the software that runs Wikipedia, and WordPress, which is used to run pretty much every blog out there. If you want to write a plugin for either of those, you'll want to learn PHP. Still, I've seen how some of those plugins work, and they're not exactly shining examples of software excellence (they seem like hacks on top of hacks).
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.
After years of promising this the fact is we are worse of today than 10 years ago because we now have different form factors. It appears the whole thing is getting worse to me and I expect soon to have a request to build a website that looks good on a clay tablet or as a tattoo on an elephant's arse.