<?php
$mysqli = mysqli_connect("<HOST>", "<USERNAME>", "<PASSWORD>", "<DATABASE>");
if (!$mysqli) {
    echo "Error: Unable to connect to MySQL." . PHP_EOL;
    echo "Debugging errno: " . mysqli_connect_errno() . PHP_EOL;
    echo "Debugging error: " . mysqli_connect_error() . PHP_EOL;
    exit;
}