CodeIgniter 4 – Create Your First Controller

In this post we will learn about Controller in CodeIgniter 4. The post will provide you code examples as well as clearly explanation.

Check the following post to learn more about CodeIgniter 4: Learn CodeIgniter 4 Tutorials.

 

What is Controller in CodeIgniter 4?

A Controller is simply a PHP class and contains public methods called action methods. It determines what response to send back to a user when a user makes a browser request.

For example:

http://your-domain.com/contact

When user makes the above request, CodeIgniter will attempt to find a Controller class named in Contact.php in app/Controllers/ directory and load it and response result to user.

 

Controller Naming Convention in CodeIgniter 4

There is a bit of naming convention when creating a Controller in CodeIgniter 4 you need to keep in mind.

  • Controller filename: The first char must be uppercase. The rest chars must be lowercased. For example:
    • Correct controller filename: Helloworld.php, Login.php, Forgotpasword.php
    • Incorrect controller filename: HelloWorld.php, ForgotPassword.php
  • Controller class name: Class name must be the same filename.

 

Create Your First Controller in CodeIgniter 4

Now it is time to create your first controller in CodeIgniter 4. For example, we will create a controller named “My First” Controller, let’s following the following steps:

  1. Create a PHP file named Myfirst.php and save it in app/Controllers/ directory.
  2. Open Myfirst.php and write the following content:
    app/Controllers/Myfirst.php
    <?php 
    
    namespace App\Controllers;
    
    class Myfirst extends BaseController
    {
        public function index()
        {
            echo 'Hello! This is my first controller';
        }
    }
    

    Now visit your site using this URL: http://localhost:8080/myfirst, you will see the Hello! This is my first controller is displayed in your browser.

Bravo! you have created your first controller, let’s move forward.

As you can see in Myfirst controller, we have created public method named index() as action method. You may be wondering why it named index and can we use another name, show for example? The answer is YES, we totally can use another action name.

In CodeIgniter, index is default action, it means when we request to http://localhost:8080/myfirst url, this url doesn’t have “action” specified, CodeIgniter then will load default index action. Let’s see the below examples for more understanding:

Request URL Loaded Controller/Action
http://localhost:8080/myfirst controller: Myfirst
action: index
http://localhost:8080/myfirst/show controller: Myfirst
action: show
http://localhost:8080/myfirst/post controller: Myfirst
action: post

Now let’s try to create another action named show as following:

app/Controllers/Myfirst.php
<?php 

namespace App\Controllers;

class Myfirst extends BaseController
{
    // ...

    public function show()
    {
        echo 'This is show() action';
    }
}

Now visit your site using this URL: http://localhost:8080/myfirst/show, you will see the This is show() action is displayed in your browser.

That’s all for your first controller. In next post, we will how you how to use View in CodeIgniter 4.

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