I find PHP easy to learn unlike VB, VBA etc. You do not need to buy books and stuff when you can learn most of it online for free. Here are some sites I always use.
I am starting to get into programming anyways forget php for now you should learn html first, anyways to get started you should buy the Lynda.com PHP with MySQL Essential Training DVD, I did and it's really helped me to get started.
easiest ways? search online for exercises or make friend with someone who knows php well
how long it takes..? hmm.. ~2 years maybe? strongly depends on how much time you are going to dedicate to learning it