PDO Mysql bağlantı hatası

<?php
$servername = "localhost";
$username = "root";
$password = "12345678";

// Create connection
$conn = new mysqli($servername, $username, $password);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 
echo "Connected successfully";
?>

<?php
$db = new PDO('mysql:host=localhost;dbname=tamirci', $root, $12345678);

?>

Warning: Unknown: failed to open stream: No such file or directory in Unknown on line 0

Fatal error: Unknown: Failed opening required 'C:/AppServ/www/PDO/bağlan.php' (include_path='.;C:\php\pear') in Unknown on line 0