For starting out, PHP. The documentation for PHP is, honestly, top notch- and you learn the language and the fundamentals of web development side-by-side (Whereas, with, say, Ruby, or Python, you have to learn the framework and the language.)
php.net is a learning resource par excellence, with a complete library, manuals, and tutorials- all of which are commented on by a peanut gallery of developers who provide sample code and important gotchas. Find PHP's manual here: http://www.php.net/manual/en/
Once you've nailed the basics of PHP development, though, you have to move on. Step up to Django, or Ruby on Rails. These frameworks are jam-packed with nigh-mandatory features that seem frustrating to learn at first, but eventually make your life as a developer much easier. Templates, the MVC pattern, database migrations, ORMs, the works. The best part is that, when you return to the wild and wooly world of PHP, all of the concepts you've learned from your framework of choice can be replicated in PHP.