Answer CodeIgniter's main features are:
Model-View-Controller Based System
Extremely Light Weight
Full Featured database classes with support for several platforms.
Active Record Database Support
Form and Data Validation
Security and XSS Filtering
Session Management
Email Sending Class. Supports Attachments, HTML/Text email, multiple protocols (sendmail, SMTP, and Mail) and more.
Image Manipulation Library (cropping, resizing, rotating, etc.). Supports GD, ImageMagick, and NetPBM
File Uploading Class
FTP Class
Localization
Pagination
Data Encryption
Benchmarking
Full Page Caching
Error Logging
Application Profiling
Calendaring Class
User Agent Class
Zip Encoding Class
Template Engine Class
Trackback Class
XML-RPC Library
Unit Testing Class
Search-engine Friendly URLs
Flexible URI Routing
Support for Hooks and Class Extensions
Large library of "helper" functions
: html_entity_decode(): Passing null to parameter #1 ($string) of type string is deprecated in