How Do I Add Months To Today’s Date In Php And Mysql?

I need to insert today’s date and today’s date + 3 months into two DATE fields in my mysql database.
I’m assuming that I use the CURDATE() function to get today’s date. How do I add 3 months to that and insert it into my database?
And what is the best reference for this type of stuff? I can’t understand php.net for some reason.