From TomatoCart Wiki

For removing error display, open the file admin/includes/application_top.php, change the following codes:
if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
} else {
error_reporting(E_ALL & ~E_NOTICE);
}
for
error_reporting(0);