I'll weigh in...
First, pick up this book:
http://www.amazon.com/dp/143022925X It comes highly recommended from a lot of PHP devs that know what they're doing ;)
Second, become intimately familiar with
http://www.php.net even the most seasoned of developers use it quite often. There's simply too many functions and mixed parameter orderings to remember it all :P
Third, implement, implement, implement. Never try and build your final product the first time around. Make a few different projects for yourself and build each one. Then go back and build each one again leveraging the knowledge you gained from the first round; you'll see how much has changed.
Fourth, find a good developer or two and ask them to review your code as a favor. Depending on the results of your review you may be able to jump right in or you may want to try building out one more mini project with your newfound knowledge and have that one reviewed as well.
Now you're ready to plan and architect your first project for production.
It's a process but that's the fastest way I know to become a proficient coder for just about any language ;)