<?php
$db_host = "localhost";
$db_user = "root";
$db_pass = "";
$db_name = "db";

try {
    /*connect as appropriate as above*/
    $db=mysqli_connect($db_host,$db_user,$db_pass,$db_name);} catch(Exception $ex) {
    echo "Cannot connect to database";
    die();
}
?>

try {
    /*connect as appropriate as above*/
    $db = new PDO('mysql:host='.$db_host.';dbname='.$db_name.';charset=utf8', $db_user, $db_pass);
} catch(PDOException $ex) {
    echo "Cannot connect to database";
    die();
}
?>