<?php
$dbhost = '';
$dbname = '';
$dbport = '';
$dbuser = '';
$dbpass = '';

try {
    $dsn = 'mysql:dbname='.$dbname.';host='.$dbhost;
    $dbh = new PDO($dsn, $dbuser, $dbpass);
} catch (PDOException $e) {
    echo '[PDO] Connection failed: ' . $e->getMessage();
}

echo '<hr>';

$conn = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
if ($conn->connect_error) {
    echo "[mysqli] Connection failed: " . $conn->connect_error;
}