wordpress data in codeigniter project

If you're going to do it REST API style, take a look at Phil Sturgeon's REST client library.  

https://github.com/philsturgeon/codeigniter-restclient

yeah both the blogs are on the same server and i dont know how to make remote  mysql access connections that u were talking about.

can i do it in this way like i know the database username and password of my wordpress blog so is there anything i can do it with this piece of information

Since both blogs are on the same server, you don't need a remote connection. You should just be able to make the connection from CI to the wordpress database. Simple to achieve just following the documentation in the user guide. I've already given you some code that should work instantly, and you'll need to find out the rest on your own. It's 1:15am here, and I've got to get to bed.

Expert Website Development - Temecula, CA
Community Auth For CodeIgniter 3