Routing – routing is responsible for responding to URL requests. Routing matches the URL to the pre-defined routes. If no route match is found then, CodeIgniter throws a page not found an exception. Controllers – routes are linked to controllers. Controllers glue the models and views together. The request for data/business logic from the model and return the results in the presentation of the view. Once a URL has been matched to a route, it is forwarded to a controller’s public function. This function interacts with the data source, business logic and returns the view that displays the results. Views – views are responsible for presentation. A view is usually a combination of HTML, CSS, and JavaScript. This is the part is responsible for displaying the web page to the user. Typically, the data displayed is usually retrieved from the database or any other available data sources.
In this tutorial, you will learn-
How to create a new CodeIgniter project
CodeIgniter Routing
Create a Route
Create a Controller
Create a View
How to create a new CodeIgniter project
We will use Composer to create a new project. I will be using the PHP built-in server, so it’s not necessary to have extra software such as Apache. In this tutorial, we are using the Windows operating system. Therefore, we have created a Sites folder on drive C. You can use any directory that is suitable for you. Open the command line/terminal and run the following command We will now create a CodeIgniter project using Composer. Run the following command HERE,
The above command creates a new CodeIgniter project version 3 using the latest stable release i.e., 3.1.9 into a directory ci-app.
When the above command has completed running, you should be able to results similar to the following in the terminal
Run the following command to browse to the newly created project directory ci-app Let’s now start the PHP built-in web server HERE,
The above command starts the built-in PHP server running on port 3000.
Open the web browser and browse the following URL: http://localhost:3000/ You will get the following page
If you can see the above page then congratulations, you have successfully installed CodeIgniter. As you can read from the above web page, the page displayed above is rendered by the view located in application/views/welcome_message.php and the responsible controller is located in application/controllers/Welcome.php
CodeIgniter Routing
For now, our application has only a single URL which is the home page. In this section, we will customize the home section. We will create some new URLs that will respond to the different requests. Let’s start with the home page route Open the routes file as indicated by the path below You should be able to see the following content HERE,
$route[‘default_controller’] = ‘welcome’; defines the default controller that responds to the URI requests $route[‘404_override’] = ”; this route allows you to define a custom route for 404 errors. A 404 error occurs when a page is not found. CodeIgniter has a default handler for the error but you can define your own if you so wish. $route[‘translate_uri_dashes’] = FALSE; this option allows you to translate dashes to underscores. We will talk about this option when we look at how routes work in CodeIgniter.
Let’s now look at the controller method responsible for displaying the home page that we saw when we opened the URL http://localhost:3000/ in the web browser. Open the following file You should be able to see the following code HERE,
Defined (‘BASEPATH’) OR exit(‘No direct script access allowed’); protects against directly accessing the controller class without passing through the index.php file. Remember, in MVC paradigm all requests have a single entry point, and for CodeIgniter, its index.php. This code blocks all requests that do not come through index.php class Welcome extends CI_Controller {…} defines a class Welcome that extends the parent class CI_Controller public function index() defines a public function that is called by default when you open the homepage $this->load->view(‘welcome_message’); this line loads the view welcome_message. The file welcome_message is located in the directory application/views/welcome_message.php
So far, we have only explored what comes out of the box with CodeIgniter, let’s now try to make some changes. We will create our home page and replace the default page Create a new file in application/views/home.php Add the following code to home.php HERE, The above HTML code loads Burma SSS framework and font from CDN network create a very basic HTML document. It applies very simple CSS rule from Burma CSS framework. Open the following URL in your browser: http://localhost:3000/ You should be able to see the following
Great, we have just successfully modified the home page. Moving on, let’s define our route. Let’s assume our application also needs to be able to show the about us page.
Create a Route
Open the routes file application/config.routes.php Add the following route HERE,
When a visitor visits the URL /about-us, we are instructing CodeIgniter to look for a controller Welcome and execute the method about_us.
Create a Controller
Let’s now define the controller method about us Open application/controllers/Welcome.php Add the following method HERE,
The above code defines a function about_us and loads a view about_us.
Create a View
Let’s now create the view that we just referenced in the above section Create a new file about_us.php in application/views/about_us.php Add the following code We are good to go, open the following URL in your web browser: http://localhost:3000/index.php/about-us You will see the following page
If you are able to see the above page then congratulations, you have successfully created a simple application in CodeIgniter.
Summary
In this tutorial, we covered three (3) major components that make up a CodeIgniter application. We looked at routes and how to define them, controllers and how to create methods that respond to route requests and created simple views that are returned to the users when they request for a resource.
