connecting project to mysql databse

Hello I’m using PHPSTORM and trying to connect my db to the project I am using this code

    <?php

$host= "localhost";
$username= "root";
$password = "";
$db_name = "test11";

$conn = mysqli_connect($host, $username, $password, $db_name);

if (!$conn) {
  echo "Connection failed!";
}
?>

It returns

Fatal error: Uncaught Error: Call to undefined function mysqli_connect() in C:Usersali_zPhpstormProjectsTectlyXsignup.php:8 Stack trace: #0 {main} thrown in C:Usersali_zPhpstormProjectsTectlyXsignup.php on line 8