Read and Write Files in CodeIgniter 4 Tutorial

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In web applications generating files, writing dynamic content over files, creating and reading files are mostly common. So here inside this article we will see such type of interesting concept in CodeIgniter 4.

Read and Write Files in CodeIgniter 4, we will do using a helper in codeigniter i.e filesystem. We will do write and read operations over a sample text file.

If you are wondering that where we should use this concept File System, So for an example if you want to make a log of your application of some kind of running processed then by using this concept you can write the log into files and then if need you can read that.

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Note*: For this article, CodeIgniter v4.1 setup has been installed. May be when you are seeing, version will be updated. CodeIgniter 4.x still is in development mode.

Let’s get started.

Download & Install CodeIgniter 4 Setup

We need to download & install CodeIgniter 4 application setup to system.

To set application we have multiple options to proceed.

Here are the following ways to download and install CodeIgniter 4 –

  • Manual Download
  • Composer Installation
  • Clone Github repository of CodeIgniter 4

Complete introduction of CodeIgniter 4 basics – Click here to go. After going through this article you can easily download & install setup.

Here is the command to install via composer –

$ composer create-project codeigniter4/appstarter codeigniter-4

Assuming you have successfully installed application into your local system.

Turn Development Mode On

When we install CodeIgniter 4, we have env file at root. To use the environment variables means using variables at global scope we need to do env to .env

Open project in terminal

$ cp env .env

Above command will create a copy of env file to .env file. Now we are ready to use environment variables.

CodeIgniter starts up in production mode by default. Let’s do it in development mode. So that while working if we get any error then error will show up.

# CI_ENVIRONMENT = production

 // Do it to 
CI_ENVIRONMENT = development

Now application is in development mode.

Load filesystem Helper

To access the write function in CodeIgniter 4, we need to load filesystem helper in application. For read operation, readfile is a php function so we don’t want helper but to write files write_file we need to load that.

We have two options to load helper in application

  • By using Parent Controller i.e BaseController.php
  • Loading inside specific controller file

Loading inside BaseController.php

Search for protected $helpers = [];

Write this code inside BaseController.

protected $helpers = ['filesystem'];

Loading Inside Specific Controller


So, here we will use by loading into BaseController.php file.

Create Routes

Open Routes.php file from /app/Config folder. Add these routes into it.

// ...

$routes->get("write-file", "Home::writeDataFile");
$routes->get("read-file", "Home::readDataFile");

Next, we need to create a controller file with name Home and two method. One is for write file and other is for read file.

Create Controller

By default Home.php controller file will be available inside /app/Controllers folder when we install CodeIgniter 4.

But if you want to create new file then you can use the same code of Home.php, only you need to modify the name of the controller class.

$ php spark make:controller Home

It will create a file called Home.php inside /app/Controllers.

Open Home.php and write this piece of code.


namespace App\Controllers;

class Home extends BaseController
	public function writeDataFile(){

		$file_content = "Welcome to Online Web Tutor Blog";

		// Type#1 - This file will be created inside /public folder
		write_file("data.txt", $file_content);

		// Type#2 - This file will be created inside /writable folder
		write_file(WRITEPATH. "data-2.txt", $file_content);

		// Type#3 - Write file inside /public folder and return value
		if (!write_file('data-3.txt', $file_content)){
			echo 'Unable to write the file';
			echo 'Successfully file written';

	public function readDataFile(){

		// Type#1 - Read file from /public folder
		$data1 = readfile("./data.txt");


		// Type#2 - Read file from /writable folder
		$data2 = readfile(WRITEPATH. "data-2.txt");

  • writeDataFile() method is for writing files. write_file is a function which we have accessed after loading filesystem helper.
  • By default file will be create and write inside /public folder of application which is at root
  • WRITEPATH returns the path of /writable folder. It is a pre defined CodeIgniter 4 constant variable.
  • readfile() is a php function. To use this, we actually don’t need to load any helper. Directly we can use it.

Application Testing

Start development server:

$ php spark serve

Open these URLs to test

Write File – http://localhost:8080/write-file

Read File – http://localhost:8080/read-file

We hope this article helped you to learn about Working with File System in CodeIgniter 4 Tutorial in a very detailed way.

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