Top 25 CodeIgniter Interview Questions and Answers

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1) Explain what is CodeIgniter?

Codeigniter is an open source framework for web application. It is used to develop websites in PHP. It is loosely based on MVC pattern, and it is easy to use compared to another PHP framework.

2) Explain what are hooks in CodeIgniter?

Codeigniter’s hooks feature provides a way to change the inner working of the framework without hacking the core files. In other word, hooks allow you to execute a script with a particular path within the Codeigniter.  Usually, it is defined in application/config/hooks.php file.

3) Explain how you will load or add a model in CodeIgniter?

Within your controller functions, models will typically be loaded; you will use the function

$this->load->model (‘Model_Name’);
4) Explain what helpers in CodeIgniter are and how you can load a helper file?

In CodeIgniter, helpers are the group of function in a particular category that assists you to perform specific functions. In CodeIgniter, you will find many helpers like URL helpers- helping in creating links, Text helpers- perform various text formatting routines, Cookies- helpers set and read cookies.  You can load helper file by using command $this->load->helper (‘name’) ;

5) Explain routing in Codeigniter?

In CodeIgniter, the way PHP files served is different rather than accessing it directly from the browser. This process is called routing. Routing in CodeIgniter gives you the freedom to customize the default URL pattern to use our own URL pattern according to the requirement. So, whenever there is a request made and matches our URL pattern it will automatically direct to the specified controller and function.

6) Why is there a need to configure the URL routes?

Changing the URL routes has some benefits like

From SEO point of view, to make URL SEO friendly and get more user visits
Hide some URL element such as a function name, controller name, etc. from the users for security reasons
Provide different functionality to particular parts of a system

7) List out different types of hook point in Codeigniter?

Different types of hook point in Codeigniter includes


8) Mention what is the security parameter for XSS in CodeIgniter?

Codeigniter has got a cross-site scripting hack prevention filter. This filter either runs automatically or you can run it as per item basis, to filter all POST and COOKIE data that come across.  The XSS filter will target the commonly used methods to trigger JavaScript or other types of code that attempt to hijack cookies or other malicious activity. If it detects any suspicious thing or anything disallowed is encountered, it will convert the data to character entities.

9) Explain how you can link images/CSS/JavaScript from a view in code igniter?

In HTML, there is no Codeigniter way, as such, it is a PHP server-side framework. Just use an absolute path to your resources to link images/CSS/JavaScript from a view in CodeIgniter




10) Explain what is an inhibitor in CodeIgniter?

For CodeIgniter, the inhibitor is an error handler class, using the native PHP functions like set_exception_handler, set_error_handler, register_shutdown_function to handle parse errors, exceptions, and fatal errors.

11) Mention what is the default URL pattern used in Codeigniter framework?

Codeigniter framework URL has four main components in default URL pattern.  First we have the server name and next we have the controller class name followed by controller function name and function parameters at the end. Codeigniter can be accessed using the URL helper. For example

12) Explain how you can extend the class in Codeigniter?

To extend the native input class in CodeIgniter, you have to build a file named application/core/MY_Input.php and declare your class with

Class MY_Input extends CI_Input {

13) Explain how you can prevent CodeIgniter from CSRF?

There are several ways to protect CodeIgniter from CSRF, one way of doing is to use a hidden field in each form on the website.  This hidden field is referred as CSRF token; it is nothing but a random value that alters with each HTTP request sent. As soon as it is inserted in the website forms, it gets saved in the user’s session as well.  So, when the form is submitted by the users, the website checks whether it is the same as the one saved in the session. If it is the same then, the request is legitimate.

14) Explain how you can enable CSRF (Cross Site Request Forgery) in CodeIgniter?

You can activate CSRF (Cross Site Request Forgery) protection in CodeIgniter by operating your application/config/config.php file and setting it to

$config [ ‘csrf_protection’] = TRUE;

If you avail the form helper, the form_open() function will insert a hidden csrf field in your forms automatically

15 )What are the features of Codeigniter? Open source framework

Light Weight
CodeIgniter is Extensible
Full Featured database classes

16) How to unset session in CodeIgniter?


17)Explain Codeigniter File Structure?

following are the folder structure:-


18)Explain MVC in Codeigniter?

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.

19) What are the helpers in Codeigniter?

Helpers, as the name suggests, help you with tasks. Each helper file is simply a collection of functions in a particular category. There are URL Helpers, that assist in creating links, there are Form Helpers that help you create form elements, Text Helpers perform various text formatting routines, Cookie Helpers set and read cookies, File Helpers help you deal with files, etc.

Unlike most other systems in CodeIgniter, Helpers are not written in an Object Oriented format. They are simple, procedural functions. Each helper function performs one specific task, with no dependence on other functions.
Loading a helper file is quite simple using the following function:


20) How will you use or add CodeIgniter libraries?

When we use the term “Libraries” we are normally referring to the classes that are located in the libraries directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create your own libraries within your application/libraries directory in order to maintain separation between your local resources and the global framework resources.

See more at

21) How to unset session in CodeIgniter?

We can use unsetuserdata to destroy particular session variable


We can use sessdestroy to destroy all session:


22) How do you use aliases with autoloading models in CodeIgniter?

We can autoload model like this:

$autoload[‘model’] = array(array(‘usersmodel’, ‘users’), array(‘newsmodel’, ‘news’), ‘categorymodel’);

23) How do you set default timezone in Codeigniter?

We can do by adding date_default_timezone_set(‘America/Los Angeles’); in index.php

24) Why is CodeIgniter called as a loosely based MVC framework?

The reason behind this is we do not need to follow the strict MVC pattern while creating an application. We can also able to build with the model only view and controllers are enough to build an application.

25) Helper vs. Library: CodeIgniter

Helpers are just small functions that help you avoid repetitive code and produce standard results.
Whereas libraries contain classes, can include different files, talk to database etc.

A library is used in object-oriented context (Controller, …), while a helper is more suitable to be used within the Views (non-object-oriented).

Helper, Plugin and Library:

Since all three methods achieve the same ends. The question then is when do you use what? Fortunately, CI has also provided that distinction in their user guide which you can go read it yourself.

For me, these are my guidelines on when to use what:

Plugins – I put all 3rd party codes I’m using in my application as Plugins. I would, as best as I can, try to use classes rather than straight function calls.

Helpers – Any standalone straight functions calls, which are repetitive in nature, I classify them as Helpers. For example, sorting functions, my own calculation functions, etc

Libraries – I classify my own classes as ‘Libraries’. Normally, if I’m already writing a class in my application, it would then to be the core logic of the application, as such, I group them all in the Library folder.