The error "The mysqli extension is missing" indicates that the mysqli PHP extension is not installed or not enabled. To resolve this issue on an EC2 instance running Ubuntu, follow these steps:

Step-by-Step Guide

Update Package List

First, ensure that your package list is up-to-date.

sudo apt-get update

Install php-mysqli Extension

Install the php-mysqli extension for PHP 7.4.

sudo apt-get install php7.4-mysqli

Verify Installation

After installation, you should verify that the extension is enabled. You can do this by creating a PHP info file.

sudo nano /var/www/html/info.php

Add the following content to the file:

php

Copy code

<?php

phpinfo();

?>

Save and close the file. Then, navigate to http://your-ec2-instance-public-dns/info.php in your web browser and check for mysqli in the output.

Restart Apache

Restart Apache to apply the changes.

sudo systemctl restart apache2