How do I read values (PHP defined constants) from wp-config.php?

Question

I need to get username, password etc from the wp-config file to connect to a custom PDO database.

Currently I have another file where I have this info, but

Answer 1

If you want to connect to DB, for current versions of PHP, using mysqli extention is recommended (mysql extention is going to deprecate):

require_once ("../wp-config.php"); // path to wp-config depends on your file locatoin
$mysqli = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
if ($mysqli->connect_errno) {
    echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
}