How To Load Database in CodeIgniter 4 Custom Library

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CodeIgniter 4 contains several libraries by default when we work with CodeIgniter 4 application. But in some cases we want some custom behaviour of libraries, so in that case custom library will be created and use. Article contains very classified information

If we need database connection inside Custom library of CodeIgniter 4, then this article will give you the complete idea about loading database and how to use. We will see the complete idea of How to load database in CodeIgniter 4 Custom Library.

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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.

Create Database

To create a database, either we can create via Manual tool of PhpMyadmin or by means of a mysql command.

CREATE DATABASE codeigniter4_app;

Successfully, we have created a database.

.env Setup

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

Either we can do via renaming file as simple as that. Also we can do by terminal command.

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.

Enable Development Mode

CodeIgniter starts up in production mode by default. You need to make it in development mode to see any error if you are working with application.

Open .env file from root.

# CI_ENVIRONMENT = production

 // Do it to 
CI_ENVIRONMENT = development

Now application is in development mode.

Database Connection

Open .env file from project root.

Search for DATABASE. You should see the connection environment variables. Give your updated details of database connection string.


database.default.hostname = localhost
database.default.database = codeigniter4_app
database.default.username = root
database.default.password = root
database.default.DBDriver = MySQLi
database.default.DBPrefix =

Now, database successfully connected with the application.

Custom Library in CodeIgniter 4

When we create a custom library in CodeIgniter 4, It will be stored into /app/Libraries directory.

Let’s create a library which simply fetch data from a employees table.

Create a Employee.php class into /app/Libraries folder. This will be custom library. Inside this library we will load database and fetch employees data from database table.

Open Employee.php file and write this code into it.


namespace App\Libraries;

class Employee
    // This function fetch data from db table
    public function getData()
        $db = db_connect(); // Load database, it loads the default database

        $tbl = $db->table("employees");

        $all_emps = $tbl->get()->getResult();

		return $all_emps;

Load Database to Library

To load database we use this given method.

$db = db_connect();

It loads default database of application.

If your application have more than 1 database. To load different database you have to do –

$db = db_connect("otherDb");

By using $db variable you can execute queries from database.

Loading Library into Controller

Let’s say we have a controller file inside application Site.php.


namespace App\Controllers;

use App\Libraries\Employee; // Load library

class Site extends BaseController
    public function getEmployeesData()
        $emp = new Employee(); // create an instance of Library

        print_r($emp->getData()); // calling method

When we call getEmployeesData(), it returns all employees data.

We hope this article helped you to learn How To Load Database in CodeIgniter 4 Custom Library Tutorial in a very detailed way.

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