Well, you can try to be a little polite as well (since generally people ARE trying to help!)
Learning PHP in 3 months is fairly doable. In fact, if you work at it you can do this faster as well!!
Building a social network in a month's time is debatable! It's been more than a decade since I have been programming in PHP, and I will not agree to take this deadline.
Btw, this is a generic answer, however in my defense so is the question! If you want more specifics on how you can get there, try asking more pointed and specific questions.