mysql - What are some of the safest ways to connect to a database with PHP?

I'm still new to PHP and MYSQL and I'm trying to learn both with modern coding techniques. All the stuff I find online seems to be outdated.

Can anybody suggest anything for me? I am also curious if the below code is outdated? If it is indeed outdated, can you suggest newer and safer methods?

    $connection = mysql_connect("localhost", "root", "");
    if (!$connection) {
        die("Oops, error happened: " . mysql_error());
    }
?>