hello,
I will make a share content(share posts or news in facebook,twitter,google+,pdf,...)with the codeigniter framework
how can I do it?

Start out using the Control Model View structure and CRUD functionality as a guide.
I would make a Controller for each main page with Create Read Update and Delete functions for the respective tables. Just make sure to keep your Controller light and pass all of the code heavy tasks to your model for processing, and also pass all returned queries from your model to a loaded view.

Let me know if this helps!