I'd say you should go for both PHP and JavaScript next - they can be complementary skills.
For JavaScript, find a jQuery tutorial (maybe on Udemy?) and work through it - it's very easy to use, but makes writing JavaScript so much less painful.
For PHP, install WAMP on your computer (I assume you're using Windows because you mentioned Notepad++ ?), then find online tutorials to lean PHP 5 and MySQL. Book-wise I recommend the Zend PHP 5 Certification Study Guide. It's not a very long book, and will take you from the basics of "what are variables and operators" to more advanced topics like how to work with databases and secure your web app.
Once you've done a few PHP and MySQL tutorials, download the Laravel framework - IMHO it's the best PHP framework currently available, and quite easy to learn. It's good to know how to do the basics in PHP (logins, database access, etc.), but once you know those a framework like Laravel will help you avoid writing the same old "boilerplate" code over and over for every project. Frameworks like Laravel have a lot of smart stuff around security, templating, etc. built-in, so all you'd have to worry about is defining your specific application's processes, not how to keep up-to-date with the latest in-depth security, encryption, and speed issues. If you're looking for books on Laravel, get Code Happy and Code Bright from leanpub.com.
Lastly, at some point you'll want to learn how to use a version control system, I recommend Git. A very simplified explanation of version control is that it allows you to "save snapshots" of what your project's codebase looked like at a given point in time. Say you only realized today that a change you made two weeks ago broke a related piece of functionality; instead of trying to remember / figure out what you changed, a version control system will tell you exactly which lines in which files changed, how they changed, and what your comments about the change were. Take a look at Github.com's video tutorials for a great introduction to Git.
If you have questions, feel free to reply here or PM me.