Could you link me to some good PHP tutorials that cover the following topics?

So, my friend who does all my PHP is busy for the next couple of days, So I have decided to finally look in to it.

I need to know how to:

* Pass variables between 3rd party scripts.
* Read variables from a MySQL database.
* Write variables to a MySQL database.
* Create functions with If and Else conditions.

Any tutorials you can link me to, or any ebooks you can name would help. thanks.