CodeIgniter (CI) does not currently support MongoDB however, CodeIgniter-MongoDB-Library library allows you to use mongodb within your CI project. This library is based on [intekhabrizvi's "Codeigniter-mongo-library"] (https://github.com/intekhabrizvi/Codeigniter-mongo-library), however that library only supports php mongo extension which is deprecated http://php.net/manual/en/mongo.setup.php.
CodeIgniter-MongoDB-Library aims to bridge that gap to allow you easily migrate to the new PHP MongoDB extension http://php.net/manual/en/set.mongodb.php if you are currently using the deprecated mongo extension. Also if you are thinking of using MongoDB for your CI project's database, this library provides a easy and clear way to integrate MongoDB with CI.
Step 1 Add PHP MongodB extension to your project using composer composer require mongodb/mongodb OR Add the following to your composer.json file "require": { "php": ">=5.3.7", "mongodb/mongodb": "^1.2" },
Step 2 Run composer install.
Step 3 Copy the contents of application into your CI's application folder.
Step 4 Edit config/mongo_db.php with your database credentials.
Step 5 Start your mongodb server
Step 6 Run the Test Controller to make sure everything is working fine.
Enjoy using this library.
Feel free to report any bugs or issues.