code send mail SMTP

 include('mail/class.phpmailer.php');

include('mail/class.smtp.php');

require_once "includes/data/mail_config.php";

SMTP Error: Could not connect to SMTP host.

==> Code chạy được và không báo lỗi

require_once 'includes/data/mail_config.php';

require_once 'classes/class.phpmailer.php';

require_once 'classes/class.smtp.php';