It is still best to start with the basics. PHP syntax, functions, and methods are different. Since Java, C# and PHP are all based on C, there are some similarities, and that will give you a leg up when jumping between those languages. However, you have to learn to walk before you can run.
Networking and entering commands via a CLI is vastly different than application programming or web development. A different method of logical thought is needed.
So with that said and from that your saying I think its best I start with a beginners books
Yes, but I'd recommend some of the books and courses that sitepoint offers:
as well as:
(Granted, this book is based on PHP 5.3, but it does a good job at introducing you to the language.)
not sure if I need to worry about PHP6
At this point, no. PHP 5.3 and MySQL 5.0.3 are the lowest common denominators these days. I've been seeing PHP 5.4 and MySQL 5.5 slowly roll out to different web hosting providers over the past few months. PHP 5.5 is out, but I haven't seen it in the wild yet. PHP 5.6 and PHP 6 are under development, but have no planned release dates, so it could be months or years before they see the light of day.