Just keep on practising. You will likely need solid HTML / CSS skills as well as PHP since the two go hand-in-hand - it's also useful to learn MySQL. Spend lots of time going through the tutorials on the excellent tizag.com as well as Lynda.
Once you're comfortable with all that and you're ready to move onto something more advanced, it's worth looking into Wordpress customisations and plugin development - that has the advantage of being pretty easy to use, with an awesome support community, and a whole bunch of mature code that you can look through yourself to get more familiar with how the language is used in the real world.
After that, try a framework like CodeIgniter or CakePHP - these are awesome for your productivity but do make sure you're comfortable with the basics first as the learning curve can be pretty steep and you want to reduce frustration as much as you can. :-) Learning design patterns will also be helpful at this stage.
One thing that will always be important to you, your users, your applications, and your potential employers is code security. I can't stress this enough. As soon as you put an application into real-world use, you have a moral and professional obligation to make that application secure. http://www.addedbytes.com/writing-secure-php/ <- read, digest, read other guides. Security is the single most important thing that a PHP developer can learn.
Above all, have fun! The best developers tend to be the ones that get genuine enjoyment out of what they're doing. You might find yourself eventually leaning in a different direction and using completely different technologies, so always keep your eyes open and be prepared to learn new things even if they don't necessarily 'fit' your current skillset. Also the more general knowledge you have about programming patterns, the better you will become in individual languages. Remember that it's an organic process so you will need to let it develop naturally - but help it along by exposing yourself to as much as possible (foreign language teachers call this 'immersion' :-) )
