CodeIgniter libraries help you do your job faster and more efficiently. Each library is really a PHP class with various methods that you can use once the library is loaded by a controller. Some classes are so useful and so ubiquitous that you might as well autoload them (such as the database and session libraries).
CodeIgniter includes the following libraries:
Benchmarking — The Benchmarking library is always active. Use it to determine the time difference between any two marked points in code and to calculate memory usage.
Calendaring — The Calendaring library must be loaded by a controller. Use it to dynamically create calendars for given months and years, with some control over formatting and appearance.
Config — The Config library is initialized automatically by the system. Use it to retrieve configuration information.
Database — The Database library is a very powerful set of methods that must be loaded. You'll be using this library so much that the next subsection of this chapter focuses on it exclusively.
Email — The Email library must be loaded. It includes a very powerful set of tools that simplifies the job of sending e-mails.
Encryption — The Encryption library must be loaded. It provides you with powerful two-way encryption methods.
File Uploading — The File Uploading library must be loaded. Use this library whenever you need to handle file uploads. It includes powerful validation features that can restrict a file by mime type, size (in kilobytes), ...