MySql vs MySqli

Basically, MySQL is the old database driver, and MySQLi is the Improved driver. The "i" stands for "improved" so it is MySQL improved.
MySQLi can be done procedural and object-oriented whereas MySQL can only be used procedurally. Mysqli also supports prepared statements which protect from SQL Injection.

MySQL extension added in PHP version 2.0. and deprecated as of PHP 5.5.0.

MySQLi extension added in PHP 5.5 and will work on MySQL 4.1.3 or above.

Connect with MySqli :-

<?php

define('DB_SERVER','localhost');

define('DB_USER','database_user_name');

define('DB_PASS' ,'db_password');

define('DB_NAME', 'db_name');

$con = mysqli_connect(DB_SERVER,DB_USER,DB_PASS,DB_NAME);

if (mysqli_connect_errno())

{

 echo "Failed to connect to MySQL: " . mysqli_connect_error();

}

?>

Connect with MySql :-

 <?php
         $dbhost = 'localhost';
         $dbuser = 'db_username';
         $dbpass = 'db_password';
         $conn = mysql_connect($dbhost, $dbuser, $dbpass);
         
         if(! $conn ) {
            die('Could not connect: ' . mysql_error());
         }
         echo 'Connected successfully';
         mysql_close($conn);
      ?>

For any quary, suggesion, advice about this topic kindly Comment below.