Getting Started in PHP
The main thing you'll need is a strong desire to learn and to improve. There are thousands of junior developers out there who frankly have poor skills and produce terrible code, and who are unlikely ever to get much better. By just displaying a reasonable amount of determination and drive, you can rise above them and become skilled and highly employable! If, on the other hand, you're not interested in becoming great, please don't start - the shallow end of the pool is full enough already.
There are three key points you'll need to bear in mind:
1) You're aiming at a moving target. The discipline of software engineering, and the PHP language, are both young and evolving.
2) Security is absolutely key to your code! Unlike 20 years (or so) ago, when I started coding in BBC Basic and the code never left the room, your site and the code on it will be out in the wild from day one, and will need to be resistant to numerous security attacks. The good news is that security basics aren't that difficult to learn.
3) You will never stop learning. And it'll (usually) be fun.
There are also three areas you'll need to study in:
Firstly, the grammar and rules of the language you want to learn, for which you can start with a basic book on PHP such as Learning PHP 5 or the slightly more advanced Programming PHP.
Secondly, the tools and techniques of software engineering. Much as you wouldn't build a house without some architectural understanding, or a car without some key ideas in mechanical engineering, your code will be immeasurably improved if you understand the best techniques to use. To a large extent, these techniques are language-independent, and will serve you well whether you end up coding in PHP, C, Java or ay other modern language. My own personal favourite book on this topic has to be The Pragmatic Programmer.
And thirdly, you'll need an understanding of the environment you're working in, both with regards to security (for which I invariably recommend Chris Shiflett's Essential PHP Security) and wider issues such as the platform you'll be running on, and the wider functionality and expectations of the web.
The good news is that it's not all book learning, and you won't be on your own. However, I've presented these books first because the community is also far keener to help someone who'll help themselves and, if you choose to splash out on professional training, it never hurts to get a head start to make the best of your investment.
So, who is out there to help you? Well, tens, possibly hundreds, of thousands of people, arranged into various types of online and real-world communities. If you're in London UK, where I am, you should join PHP London; sign up to the mailing lists and join us at the social meets. If you're elsewhere, take a look at PHP User Groups or MeetUp.com to find a local group.
Does that feel a bit too much like jumping in at the deep end? Don't worry about that. These communities are here to support you at all levels, and as per this recent piece by Chris Cornutt, you're unlikely to become a great developer on your own. We could save you a few years of confusion, and do wonders for your skills and earning power!
If you do want to go for professional coaching, the best place to go in the UK is probably iBuildings, who are Zend's partners for the UK and Netherlands. They can provide a range of training for various skill levels - I and my team took some a few months back and found it very useful. However I should probably disclaim here that I've since become friends to a few of the iBuildings staff, and I will (much as Paul will hate me for admitting this) point out that you can become a good developer without their help! For individuals in particular, the training can be quite an investment, and so self-study can be a good option.
So, where (and how) to self-study? Well, as you're reading this I presume you're already familiar with various blogs and online sources, but I'll point out that PHP London has a collected RSS feed (including this blog) at http://feeds.feedburner.com/PHPLondon, and you'll find many more blogs at Planet PHP. Another good resource is the hardcopy (and recently relaunched) PHP|Architect magazine, which is a must at its new price.
Personally, I find self-study most productive when I have a goal. One I'd particularly recommend would be the Zend PHP5 Certification. This is not a basic certification (for that, look at something like BrainBench), and may take you a year or two to learn enough to pass if you're new to programming, but that's precisely what makes it useful. If you can pass this, you probably know what you're doing. Note that while there is a study guide for the certification, it's not enough to refer to this book alone as it's mainly a syllabus - you'll need to study from other resources to pass.
Well, I figure that that should get you started! As ever, do feel free to comment or drop me a line with any ideas or queries.