xxamp won't connect to my database

I want to test some codes using xxamp but I keep getting no database selected even though it is right, any ideas why it won't connect to the database?

<?php
$host = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";
$connection = mysqli_connect($host,$username,$password,$database);
if($connection === false) {
}
?>