notify after event in followed node by follower I use the Flag module in Drupal 7, and created a flag (for nodes) with  "follow" as name of the flag.

I want to add new event on the followed content by user, send notify for follower by php code or display counter of new event unread to user.

How can I do this?
If i understand you right, you want to do something after a user was flagged... 

The flag module has a full Rules module integration.
This module gives you the ability to react to specific events (like flagging a user) and do actions like showing a message, sending a email, or execute some custom php-code.