Firstly, all the best with learning PHP! It's a fabulous tool that can produce some great results.
Now, a few things to bear in mind...
Firstly, be aware that PHP is a moving target. version 5 is current, but relatively recent. v4 is still commonly used. And you might even still find some tutorials for PHP3.
Be very careful that the techniques you learn are applicable to current versions of PHP. The language has changed quite a bit between versions (for the better, I should add), and some techniques that were standard practise in PHP3 and 4 are obsolete or discouraged in PHP5.
Secondly, take time to learn about web site security. PHP is a great tool, but like any other programming language, it is possible to use it to write really bad code. Sometimes that's okay, but on the web, you need to keep your site secure. Simple programs shouldn't have many problems, but as you learn to write more complex programs, watch out that you don't open yourself up to being hacked.
And finally, as someone else has already said, the very best resource for learning PHP is the PHP site itself. It's got one of the best online manuals I know of.