Where can i fully learn PHP coding?

I have my own game site, yes its going very well but im oftenly getting my mates to help out on the coding, i can edit a few things but cant actually code.
I was wondering if anyone knew any sites where i can fully learn PHP coding from the basics to the real thing,

Thanks.

By far the best site to learn from is the official documentation on php.net

Link: http://php.net/manual/en/index.php