What is CodeIgniter?

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Welcome to CodeIgniter

CodeIgniter is an Application Development Framework – a toolkit – for people who build web sites using PHP. Its goal to enable you to develop projects much faster than you could if you were writing code from scratch, by providing a rich set of libraries for commonly needed tasks, as well as a simple interface and logical structure to access these libraries. CodeIgniter lets you creatively focus on your project by minimizing the amount of code needed for a given task.

Who is CodeIgniter For?

CodeIgniter is right for you if:

  • You want a framework with a small footprint
  • You need exceptional performance
  • You need broad compatibility with standard hosting accounts that run a variety of PHP versions and configurations
  • You want a framework that requires nearly zero configuration
  • You want a framework that does not require you to use the command line
  • You want a framework that does not require you to adhere to restrictive coding rules
  • You do not want to be forced to learn a templating language
  • You eschew complexity, favoring simple solutions
  • You need clear, thorough documentation

CodeIgniter at a Glance

    • CodeIgniter is an application framework
    • CodeIgniter is free
    • CodeIgniter is Light Weight
    • CodeIgniter is fast
    • CodeIgniter uses M-V-C
    • CodeIgniter generates Clear URLs
    • CodeIgniter packs a punch
    • CodeIgniter is extensible

*use your own libraries, helpers, or through class extensions or system hooks.

  • CodeIgniter Doest Not Require a Template Engine
  • CodeIgniter is Thoroughly Documented
  • CodeIgniter has a Friendly Community of Users

CodeIgniter Server And Database Support

PHP version 5.1.6 or newer. A Database is required for most web application programming. Current supported databases are MySQL (4.1+), MySQLi, MS SQL, Postgres, Oracle, SQLite, and ODBC.

CodeIgniter Features

  • 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

Application Flow Chart


Model – View – Controller , as the name implies, is a design pattern that allows developers to cleanly separate their code into three categories

  • Models – Maintain data
  • Views – Display data and user interface elements
  • Controllers – handles user events that affect models and views

CodeIgniter is based on the Model-View-Controller development pattern. MVC is a software approach that separates application logic from presentation. In practice, it permits your web pages to contain minimal scripting since the presentation is separate from the PHP scripting. The Model represents your data structures. Typically your model classes will contain functions that help you retrieve, insert, and update information in your database. The View is the information that is being presented to a user. A View will normally be a web page, but in CodeIgniter, a view can also be a page fragment like a header or footer. It can also be an RSS page, or any other type of “page”. The Controller serves as an intermediary between the Model, the View, and any other resources needed to process the HTTP request and generate a web page. CodeIgniter has a fairly loose approach to MVC since Models are not required. If you don’t need the added separation, or find that maintaining models requires more complexity than you want, you can ignore them and build your application minimally using Controllers and Views. CodeIgniter also enables you to incorporate your own existing scripts, or even develop core libraries for the system, enabling you to work in a way that makes the most sense to you.

Goal Of CodeIgniter

Our goal for CodeIgniter is maximum performance, capability, and flexibility in the smallest, lightest possible package. To meet this goal we are committed to benchmarking, re-factoring, and simplifying at every step of the development process, rejecting anything that doesn’t further the stated objective. From a technical and architectural standpoint, CodeIgniter was created with the following objectives: Dynamic Instantiation. In CodeIgniter, components are loaded and routines executed only when requested, rather than globally. No assumptions are made by the system regarding what may be needed beyond the minimal core resources, so the system is very light-weight by default. The events, as triggered by the HTTP request, and the controllers and views you design will determine what is invoked. Loose Coupling. Coupling is the degree to which components of a system rely on each other. The less components depend on each other the more reusable and flexible the system becomes. Our goal was a very loosely coupled system. Component Singularity. Singularity is the degree to which components have a narrowly focused purpose. In CodeIgniter, each class and its functions are highly autonomous in order to allow maximum usefulness. CodeIgniter is a dynamically instantiated, loosely coupled system with high component singularity. It strives for simplicity, flexibility, and high performance in a small footprint package.

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