Whenever I'm trying out a new language, I usually check if lynda.com has a tutorial on it. I happen to know that lynda.com does have one on PHP, and if you learn well with video tutorials, you can get to a pretty good spot with those tutorials in record time. If I remember right (It was a long time ago last time I looked at them), they don't get into OOP much, but if you're coming from C++ and Java, the php docs should probably be enough to help out.
Once you've got the basics down, the best way to learn would be to come up with a simple project and hack away at it. Build a tiny CMS or a blog, php is flexible, so you can come up with your own style pretty quickly, and then learn from your mistakes.
I highly recommend the PHP official tutorial on their site. I learned PHP more than 10 years ago, and it is great. Second maybe to the Flash tutorial that comes with Flash.
It could also be useful to try and use PHP however you can, start writing shell scripts with it, go and observe the source code of PHP sites and applications you like.
