Would this login function be secure?

Question

Would this login function be secure, I put the url data straight into the function, but would this be unsafe? Could this be injected, I know it has no SQL, but is it venerable?

if ($_SERVER["REQUEST_METHOD"] == "POST") {    
    $login = check_login($_POST['emailusername'], $_POST['password']);
    if ($login) {
        // Registration Success
       header("location: /");
    } else {
        // Registration Failed
        echo 'Username / password wrong';
    }
}

function:

// CHECK LOGIN SCRIPT
   function check_login($emailusername, $password) 
    {

$host = 'localhost';
$port = 3306; // This is the default port for MySQL
$database = 'example';
$username1 = 'root';
$password1 = 'root';

$dsn = "mysql:host=$host;port=$port;dbname=$database";
$db = new PDO($dsn, $username1, $password1);

                $password = md5($password);


$statement = $db->prepare('SELECT uid FROM users WHERE (email = ? or username = ?) and password = ?');
$statement->execute(array($emailusername, $emailusername, $password));

if ($result = $statement->fetchObject()) {
    $_SESSION['login'] = true;
    $_SESSION['uid'] = $result->uid;
    return TRUE;
}else{
    return FALSE;
}    }

Answer 1

I don't see a reason why it would be unsecure, but I'd suggest you to follow authentication best practices though.