Are you absolutely set on learning PHP? If you are, then buy a good book - there's several mentioned here that are actually ok - but please, learn the security aspects from the start. There's more than enough PHP developers in the world who are writing insecure code (I used to be one of them, so I'd know).
Practice is key though; I've been programming in PHP now for about 6 years, and I'd consider myself fairly competent (I passed my Zend PHP5 Certification a couple of months back), but I still find functions I've never seen before.
A tip - don't even think of looking at Zend Framework, Magento or anything like that until you're comfortable with the basics. If you do, you'll definitely struggle; they use some advanced concepts which even I find it hard to wrap my head around at times.
Alternatively, you could learn something else...
