File structure in CodeIgniter
After unzipping the CodeIgniter folder you will get a file hierarchy of CodeIgniter files as shown below.
CodeIgniter file structure is mainly divided into three parts:
Application folder is the main development folder for you where you will develop your project. It contains your models, views, controllers, configuration and many other files. It contains all the code of the project you are working on.
Look at the above snapshot, autoload.php file will load your libraries, helpers or you can define custom files so you don't have to call them again and again in your project. In config.php file we set our base-url etc. In database.php file we need to configure our database setting to connect it from our project. In routes.php file you can set your default controller page.
Name of the controller class file will always start with an uppercase letter. For example, it will be named like Main.php and not main.php.
Generally, there will be no need to change these classes, but in case if you are modifying a class, create a class in "application/core" folder having same name as the core class file name in "system" folder.
$this->load->helper('form'); will create a form that will work perfectly with CodeIgniter. And
$this->load->helper('date'); will get you date features in your applications.
All action of CodeIgniter application happens here. It contains files which makes the coding easy.
It is the offline CodeIgniter guide. It comes with every CodeIgniter downloaded version. In case of any query, you can read its user guide. You can learn here all the functions, libraries, helpers of CodeIgniter. Before starting use of CodeIgniter go through this guide once.
Last but not least, you can see a file index.php. Here we can set application environment and error level. It is better not to touch this file if don?t have sufficient knowledge.