If your Photo Cart is suddenly getting a 500 error or only displaying a blank page then you or your hosting company has updated the PHP (programming language) to PHP 7 which Photo Cart is not compatible with (and will not be compatible with) mainly because of the removal of the my_sql functions which are replaced with my_sqli functions.
You would need to have the PHP version downgraded to 5.6 in order for Photo Cart to work. If downgrading the PHP doesn't work then you may have to update Photo Cart to the last version of 7. Download Photo Cart 7 upgrade files. Upgrade instructions.
Server Mail Settings - Php Mailer Path
Absolut Path or relative Path?
Path includes php File oder exlude?
Test it all and became every time i push the "send test email" an white Page and no email will be send.
$smtp_phpmailer_url = "".$site_setup['smtp_phpmailer_url']."";
You can read more about how include_once locates the file at http://php.net/manual/en/function.include-once.php.
Loading more pages