from regestarion database in php Login and password

php 

<?php
$db_name="registration";
$mysql_username="root";
$mysql_password="";
$server_name="localhost";
$conn=mysqli_connect($server_name,$mysql_username,$mysql_password,$db_name);
if($conn){
echo"<h3>connection successful</h3>";
}
else{
echo"<h3>no connection</h3>".mysqli_connect_error();
}
?>