What is the good source to learn PHP online?

I prefer original source: http://www.php.net/[^].
Yes, it's good enough for learning as well.

A note: PHP is pretty sloppy cheap language and a pretty sloppy project, but knowing it makes sense, mostly due to faith in this language taken my most Web hosting providers. However, be careful if you're are inexperienced in languages: PHP can cause brain damage, one way to immune yourself would be learning something more serious first.

—SA

in addition to Pong D.Panda and SA answer you can also navigate there[^] to learn PHP on line.