It really depends on what you are looking for, how experienced you are and what your objectives are. My recommendation is that you dive straight into OOP without going for procedural coding as going procedural is the lazy way. There's loads of tutorials out there, I've completed a few from W3 Schools (http://www.w3schools.com/php/default.asp) lately, but PHP.net have some great resources here: http://php.net/manual/en/tutorial.php. I find the PHP.net tutorials can dive into some pretty advanced stuff though. As I say, it's trial and error, it really depends on your experience and what you want to get out of it.
Register @ w3school.com . Bundles of PHP tutorials and exercises available. You can also participate to the PHP forums where PHP developers are active.
W3schools.com is the best online php tutorial however you have to take help of an experienced programmer to learn php perfectly..Tutorial have some limitations and they may not provide what you need..