cara membuat script PHP untuk koneksi database?

<?php
$servername = "localhost" ;
$username = "username" ;
$password = "password" ;
$db_name = "nama_db";

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

if (!$conn) {
die("Connection failed:" . mysqli_connect_error());
}
echo "Connected successfully" ;
?>

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#Semoga bermanfaat ^_^