Top 40 CodeIgniter Interview Questions and Answers

CodeIgniter is a powerful PHP-based web development framework that was created by EllisLab in 2006. Though in 2014 it entered into a stewardship of British Columbia Institute of Technology, this was taken up by CodeIgniter Foundation in 2019.

CodeIgniter Open Source is a PHP MODEL VIEW CONTROLLER (MVC) framework that is helpful for developers who want a simple and decent toolkit to create full-fledged web applications. It provides libraries to connect to the database and perform multiple functions like session management, sending emails, and file uploads.

Working with CodeIgniter requires PHP experience since it is built on PHP’s framework. With Web Development prospects on rise, the need for skilled Codeigniter engineers are more than they have ever been. The following CodeIgniter Interview Questions are aimed to help a candidate preparing for these job positions to build a solid base and also give them a fair idea of what they can face.

First, let’s look at some commonly asked CodeIgniter Interview Questions.

Compare these job interview questions with a competing set of Laravel Interview Questions to get a comprehensive idea of open-source, PHP based, fast-development frameworks. Conceptual CodeIgniter Interview Questions often act as deciding factors for recruiters while choosing individuals for their web development/Codeigniter positions.

Q1. HOW DO WE DEFINE CODEIGNITER?

Ans. CodeIgniter is an open-source PHP framework responsible for the development of web applications. This framework is based on MVC Architectural design. 

Q2. LIST SOME FEATURES OF CODEIGNITER?

CodeIgniter Interview Questions like these require simple and to the point answers with one or two liners describing each point. It is recommended not to over-explain a single point or give no explanation at all. Precision and shorter descriptions comprise a winning formula.

Ans. Following are some features of CodeIgniter:

• OPEN-SOURCE: Codeigniter is open-source and is backed by Open Software License (OSL).
• SMALL FOOTPRINT FRAMEWORK: The entire source code for the CodeIgniter framework is only around 2MB.
• BLAZING FAST: CodeIgniter takes only seconds to load right after installation.
• CLEAR DOCUMENTATION: The framework is well-documented with apt books, in-depth tutorials, and forum questions with proper answers on CodeIgniter. This means that regardless of the problems the user is facing, someone might have found the problem and solved it, and there is already a solution.
• APPLICATION SPECIFIC COMPONENTS THAT ARE BUILT-IN: It has components for giving emails, management of databases, management of sessions, etc. Built-in functions are designed to operate independently without over-reliance on other components, making maintenance easier.
• SIMPLE SOLUTIONS: It encourages MVC but doesn’t force it on the user.
• STRONG SECURITY: CodeIgniter protects against Cross-Site Request Forgery and XSS (cross-site scripting) attacks.
• EXTENDABLE: Users can easily extend the system by using Libraries, Helpers.

Q3. WHICH IS THE NEWEST VARIANT OF CODEIGNITER? 

Ans. 4.1.3 is the edition of the CodeIgniter framework. This version was released on June 6th, 2021. This is probably among the most common CodeIgniter Interview Questions and applicants are advised to be abreast of the latest releases to be able to successfully answer this.

Q4. WHICH IS THE STABLE VERSION OF CODEIGNITER? 

Ans. 4.1.1 is the stable version and it was released on February 1st, 2021.

Codeigniter Interview Questions like these should be dealt with caution. It is common to mix up between the latest release and the latest ‘stable’ release.

Next, we look at CodeIgniter Interview Questions that focus on the architecture of CodeIgniter and go into detail about the entire MVC framework.

Q5. EXPLAIN CODEIGNITER ARCHITECTURE.

Ans. When a request comes from the CodeIgniter application, it will first go to the index .php page to routing to decide whether the request passes through cache or a security check. If the requested page doesn’t exist in the cache file, then routing will pass the request to security check. After testing the security check, the registered page will go to the application controller. The application controller is used to load the files like libraries, Models, Helpers, Plugins, and Scripts and then pass them to the View. A view is used to fetch the data from the application controller that will be presented to the user.

Q6. HOW DO YOU CHECK THE VERSION OF CODEIGNITER YOU ARE USING?

Ans. Users can check the version of CodeIgniter by two methods:

2. By navigating to the system /core/CodeIgniter.php directory and run the following code:

define(‘CI_VERSION’,’2.1.4’);

Q7. WHICH DATABASES CAN BE USED IN CODEIGNITER?

Ans.  Commonly asked CodeIgniter Interview Questions will feature this topic- Following are the most common databases that can be used with CodeIgniter:-

• MySQL
• ORACLE
• SQLite
• ODBC
• FIREBIRD
• CUBERID etc.

Q8. EXPLAIN THE MVC STRUCTURE OF CODEIGNITER.

Ans. MVC stands for MODEL VIEW CONTROLLER. Model View Controller separates application logic from the presentation layer. It helps web pages to contain minimum scripting.

• MODEL: It is used to represent data structures. Model classes constitute functions that help to insert, retrieve, and update information in the database.
• CONTROLLER: It acts as an intermediary between the view, model, or any other resource to process HTTP requests. The Controller controls the whole application by URI.
• VIEW: It represents the information that is being presented to the user. In CodeIgniter, a View could be a simple or complex webpage. The web page contains a header, footer, sidebar, etc. A view cannot be called directly.

Next set of CodeIgniter Interview Questions delve into the concept of a model, its uses and other related concepts.

Q9. EXPLAIN THE BASIC STRUCTURE OF A MODEL?

Ans. Models are PHP classes that are designed to work with information in the database. Model classes are stored in application/models/directory.

The Basic Prototype for a model class is:

  class Model_Name extends CI_Model

Here Model_ Name implies to Name of Class.

NOTE: 

• The first Letter of the class name must start with an upper-case letter with the rest of the name lowercase.
• Make Sure the class extends the base Model Class.
• The File Name must match the class name.

Q10 HOW DO YOU LOAD A MODEL IN CODEIGNITER?

Ans. Models can be loaded and called from within the controller methods.

The following method is used to load a model:

  $this-> load ->model ->(‘model_name’);

If the model is in a sub-directory, replace ‘model_ name’ with the path of the sub directory.

Example: 

If your model is in application/models/placeholder/name.php, then you must put ‘placeholder/name’ inside the parenthesis.

Q11. HOW TO AUTO-LOAD A MODEL?

Ans. If the user needs a particular model globally throughout the application, the user can tell the CodeIgniter to autoload it during system initialization.

This can be done by opening the application/config/autoload.php file and adding the model to the autoload array.

Q12. HOW WOULD YOU CONNECT MODELS TO A DATABASE AUTOMATICALLY?

Ans. CodeIgniter Interview Questions will have this listed as an important query. Loading a model doesn’t connect to the database automatically. There are different methods to connect a database:-

Auto Connect: This feature automatically loads the database with every page load. To enable auto-connect, go to application/config/autoload.php and add word database to library array.

Manually Connecting Database: If the user wants to connect the database only to some pages of the project, the user can use the following code:

$this->load->database ();

Q13. HOW TO LOAD A VIEW IN CODEIGNITER?

Ans. A View cannot be loaded directly. It must be called by a controller. A View can be loaded using the following code: 

  $this->load->View(‘name’)

NOTE: 

• The page name should be written in brackets.
• Don’t specify .php unless you are using some other extension.

Q14 WHAT IS A CONTROLLER IN CODEIGNITER?

Ans. A Controller acts as an intermediary between the model and the view to process the HTTP request. Controllers receive input from the user and determine what to do with the input- whether passing the data to a model to save or requesting the data from the model which is passed on to the view to be displayed. The name of the controller class file is directly associated with the URL. The name of the controller class must start with an uppercase letter. The controller must be called with a lowercase letter.

Q15. WHY CODEIGNITER IS CALLED AS LOOSELY BASED MVC FRAMEWORK?

Ans. CodeIgniter is called a loosely based framework because in this, the controller is the necessary element, but Model and Views are not mandatory. In other words, users can build a website without a Model. Moreover, users can modify CodeIgniter to utilize HMVC as well.

Libraries and Helpers are important concepts an interested applicant should be aware of. This is reflected in the CodeIgniter Interview Questions based on these two keywords alone and their different uses in the overall framework. Job Interview Questions like these on CodeIgniter Open Source framework should be part of preparatory steps while applying for these Web Development positions.

CodeIgniter Interview Questions on Helpers:

Q16. EXPLAIN HELPERS IN CODEIGNITER?

Ans. Helpers help the user to accomplish the task. These are basically a collection of simple and substantive functions. Each performs one specific job. Helpers are independent of each other and they are not written in object-oriented format. Once live, it becomes universally available in the controller section and view section. This is a useful tool asked during CodeIgniter Interview Questions.

Q17. EXPLAIN DIFFERENT TYPES OF HELPERS?

Ans. Different types of helpers are as follows:

• FILE HELPER: It helps to deal with the file.
• TEXT HELPER: This is used to perform various text formatting routines.
• FORM HELPER: It helps in creating form elements.
• COOKIE HELPER: set and real cookies 
• URL HELPER: It assists in creating links.

Q18. HOW DO YOU LOAD A HELPER FILE ALSO EXPLAIN HOW TO LOAD MULTIPLE HELPER FILES?

Ans.

$this->load->helper(‘file_name’);

Where file_ name is the file name of the helper.

To load URL Helper, use

$this->load->helper(‘url’);

A Helper can be inserted anywhere.

If the user wants to load multiple helpers, then the user needs to specify them in an array. This can be done by using the following method:

$this ->load->helper(array(‘Helper1′,’Helper2′,’Helper3’));

Here Helper 1,2,3 represents different helper’s names.

CodeIgniter Interview Questions on Libraries:

Q19. WHAT IS A LIBRARY IN CODEIGNITER?

Ans. Libraries are packages that provide high-level abstractions. CodeIgniter provides a rich set of libraries. Libraries increase the speed of an application. The library is located in the System/Library.

Q20. HOW DO YOU LOAD A LIBRARY IN CODEIGNITER?

Ans. Libraries can be loaded by using below code:

$this->load->library(‘Class_Name’);

Where Class_Name represents the name of the library.

Multiple Libraries can also be loaded by using following code:

$this->load->library->(array(‘library1′,’library2’));

Q21. HOW DO YOU CREATE A LIBRARY IN CODEIGNITER?

Ans. CodeIgniter Libraries are stored in the System folder. Users can also create a new library inside the application/Libraries folder by coding. This is done to separate local and global framework resources.

Libraries can be created by using 3 methods:

• Creating an entirely new library.
• Extending Native Library.
• Replacing Native Library.

NOTE:

• Capitalize the first letter of all file names.
• Class name first letter must be an uppercase letter.

The file name and class name should be the same.

Q22. DIFFERENTIATE BETWEEN LIBRARY AND HELPER?

Ans. LIBRARY 

• The Library is a class. So, the user needs to make an instance of the class to use it.
• Libraries are located under System/Libraries.
• It is object-oriented.
• A library can be loaded using $this->load->library (‘library name’).
• To call library functions, the user needs to create an object of the class.

HELPERS 

• A Helper is a file that has PHP functions.
• Helpers are located under System/Helpers.
• These are not written in an object-oriented format, hence the user can simply call helper functions.
• A Helper can be loaded using $this->load->Helper (‘helper name’)
• Helpers can be called in the same way you call PHP functions.

CodeIgniter Interview Questions on Hooks:

Q23. WHAT ARE HOOKS IN CODEIGNITER?

Ans. Hooks allow the user to execute a script with a particular path within the CodeIgniter. It allows you to change the inner working of the framework without changing the core files. Hooks are defined in application/config/hooks.php file.

Q24. HOW DO YOU ENABLE HOOKS IN CODEIGNITER?

Ans. Hooks can be enabled by navigating to the application/config/config.php file and switch the following setting to ‘TRUE’ as shown below –

$config[‘enable_hooks’] = TRUE;

Q25. LIST VARIOUS TYPES OF HOOK POINTS IN CODEIGNITER?

Ans. 

• pre_system: It is called much before the system execution. At this point, only hook class and benchmark must be loaded.
• pre_controller: It is called immediately before any of the controllers being called. At this point, all the classes, security checks, and routing must be done 
• post_controller: As the name suggests, it is called immediately after the controller is completely executed.
• post_controller_constructor: This is called after your controller is instantiated but before any method calls happen.
• cache_override: It allows the user to call functions in the output class.
• display_override: It is used to send the final page at the end of the final execution.
• post_system: It is called after the final page is sent to the browser at the end of the system execution.

Q26. HOW CAN WE CONFIGURE HOOKS IN CODEIGNITER?

Ans. Hooks can be globally enabled or disabled by setting in the 

application/config/config.php

It can be defined in 

application/config/hooks.php page

CodeIgniter Interview Questions on Security, SQLs and other concepts:

Job interview questions on these topics are very important in today’s day and age. Security, especially about cross-site scripting – the most common vulnerability in the web apps today, is sought after in most CodeIgniter Web Developer/Engineers by organizations, and it is imperative to include these in the preparatory stack of CodeIgniter Interview Questions.

Q27. WHAT IS AN INHIBITOR? 

Ans. An Inhibitor is an error handling class in CodeIgniter. Inhibitor uses the native PHP functions to handle parse errors, exceptions, and fatal errors. These native PHP functions are as follows:

• set_exception_handler
• set_error_handler
• register_shutdown_function

Q28. WHAT ARE DRIVERS IN CODEIGNITER. ALSO, EXPLAIN HOW DO YOU INITIALISE A DRIVER IN CODEIGNITER?

Ans. Drivers are special types of the library that has a parent class and multiple child classes. Child Classes can access the parent class but do not have access to a sibling class. Drivers are found in the system/libraries folder in the CodeIgniter folder.

 To make use of a driver in CodeIgniter, the user must initialize it inside the controller by using the following code:

$this->load->driver(‘Class_Name’);

Q29 HOW DO YOU CREATE A DRIVER IN CODEIGNITER?

Ans. Drivers can be created by using three steps:

• Create a file name such as ‘Driver_name.php’.
• Create a driver list inside the file.
• Write the code for each individual driver.

Q30. WHAT IS THE BASIC CODEIGNITER URL STRUCTURE?

Ans. CodeIgniter uses a segment-based approach. Its URL structure is:

abc.com/class/function/ID

Where class: controller class.

Function: the method that is called.

ID: additional segment which is passed to the controller.

Q31. WHY DO URL ROUTES NEED TO BE CONFIGURED?

Ans. URL Routes needs to be configured because of the following reasons:

• To improve the number of page visits.
• To hide the code complexities from the user.

Q32. WHAT ARE CODEIGNITER SECURITY METHODS?

Ans. CodeIgniter Security methods help in creating a secure application. It has several ways of implementing security in the web application and protecting the raw input data fed to your program. Following are the CodeIgniter security methods:

• XSS filtering (Cross-Site Scripting)
• CSRF (Cross-Site Request Forgery)
• Class-Reference.

Q33. EXPLAIN HOW CSRF CAN BE ENABLED (CROSS-SITE REQUEST FORGERY) IN CODEIGNITER?

Ans. CSRF can be activated by operating 

application/config/config.php file and setting it to

     $ config [‘csrf_protection’] = TRUE;

Q34. HOW DO YOU PRINT A SQL STATEMENT IN CODEIGNITER MODEL?

Ans. Users can print a SQL statement by using the following code:

$this>db>insertid();

Q35. HOW DO YOU CALL A CONSTRUCTOR IN CODEIGNITER?

Ans. A Constructor can be called by using the following syntax:

  parent:___construct();

Q36. DESCRIBE ORM? LIST SOME ORM’s FOR CODEIGNITER?

Ans. It stands for Object Relational Mapping. It is a programming technique for converting data between incompatible type systems using OOPs (Object-Oriented Programming Language). CodeIgniter Interview Questions will determine your knowledge on this topic.

Following are the ORM’s supported by CodeIgniter:

• Data Mapper: It is an object relational mapper which is written in PHP for CodeIgniter. It is curated to transform database tables into easy-to-use objects that are fully aware of the relationships between them.
• Doctrine: It contains tutorials, a reference section, and cookbook articles that help to explain the different parts of the object-relational mapper.
• Gas ORM: Gas ORM is easy to use and a lightweight object-relational Mapper for the CodeIgniter. This was specifically built for the CodeIgniter app. It uses CodeIgniter database packages, a powerful DBAL that supports multiple database drivers. 

Q37. EXPLAIN XSS FILTERING IN CODEIGNITER?

Ans. XSS, also known as Cross-Site Scripting – is used to disable those codes which try to hijack cookies and perform other malicious activities.

XSS filtering converts data to character entities if it encounters anything harmful. It uses the xss_clean() method to filter data.

  $data= $this->xss_clean($data);

This filtering is also used to test images for XSS attacks. When this parameter is set to TRUE, it will not return an altered string. It returns TRUE if the image is safe and FALSE if it contains malicious information.

Q38. EXPLAIN HOW CODEIGNITER CAN BE PREVENTED FROM CSRF ATTACKS (CROSS-SITE REQUEST FORGERY)?

Ans. There are multiple methods to protect CodeIgniter from CSRF attacks. But one of the most effective methods is to use Anti-CSRF Tokens. In this method, users can use a hidden field in each form on the website. This is known as CSRF Tokens. CSRF token is a random value that changes with each HTTP request sent. When it is inserted into the website forms, it gets saved in the user’s session as well. So, when the form is submitted by the user, the website confirms whether it is the same as the one saved in the session. If it matches, then the request is legitimate. The token value changes each time the page is loaded, which makes it tough for the hackers to guess the current token.

Q39. EXPLAIN WHAT A CSRF ATTACK IS AND HOW IT CAN BE ENABLED IN CODEIGNITER?

Ans. CSRF (CROSS-SITE REQUEST FORGERY) is an attack that forces an unauthenticated user to execute unwanted actions on a web application. This CSRF attack is very common attack. It is considered a sleeping giant in the web application world.

User can activate CSRF protection in CodeIgniter by operating application/config/config.php file and setting it to 

     $config[‘csrf_protection’] = TRUE;

If the user wants to make use of the form helper, the form_open() function will insert a hidden CSRF field in your forms automatically.

Q40. EXPLAIN HOW IMAGES/CSS/JAVASCRIPT CAN BE LINKED FROM A VIEW IN CODEIGNITER?

Ans. In CodeIgniter, Images/CSS/JavaScript can be linked from a View by using an absolute path. It is as follows:

/css/styles.css

/js/query.php

/img/news/566.jpg

CONCLUSION 

In conclusion, the set of CodeIgniter Interview Questions presented here summarize the type of queries that aspiring web developers can face in their job seeking conquest. To have a solid PHP and web development foundation is key; Combining these job interview questions with the right kind of knowledge, and added insight in one’s repertoire, e.g. with Laravel interview questions – would result in an increased propensity to land a job in this world of heavy competition.

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