[Andreas]

New Bug: Version 1.2 will cause a fatal PHP error if build_user_subscription() is called more then due to redefined functions.

A few suggestions

PHP Code:

    foreach($_POST as $key => $value){
            $ds[$key] = $value;
        }
        $vbulletin->input->clean_array($ds, array(
            'send_pm_global' => TYPE_NOHTML,
            'send_em_global' => TYPE_NOHTML,
            'pm_from_global' => TYPE_NOHTML,
            'send_pm_paidsub' => TYPE_NOHTML,
            'pm_title_paidsub' => TYPE_NOHTML,
            'pm_message_paidsub' => TYPE_NOHTML,
            'send_em_paidsub' => TYPE_NOHTML,
            'em_subject_paidsub' => TYPE_NOHTML,
            'em_body_paidsub' => TYPE_NOHTML
        )); 


Why not just

PHP Code:

$vbulletin->input->clean_array_gpc('p', array(
    'send_pm_global' => TYPE_NOHTML,
    'send_em_global' => TYPE_NOHTML,
    'pm_from_global' => TYPE_NOHTML,
    'send_pm_paidsub' => TYPE_NOHTML,
    'pm_title_paidsub' => TYPE_NOHTML,
    'pm_message_paidsub' => TYPE_NOHTML,
    'send_em_paidsub' => TYPE_NOHTML,
    'em_subject_paidsub' => TYPE_NOHTML,
    'em_body_paidsub' => TYPE_NOHTML
)); 


PHP Code:

$db->query_write("UPDATE " . TABLE_PREFIX . "datastore SET data='" . $db->escape_string(slw_serial($ds)) . "' WHERE title='pmnotify'"); 


You should never UPDATE table datastore directly, as the user might use a datastore cache - and thus your updated data will not be in the cache (until it gets cleared).
Use build_datastore() instead.

PHP Code:

$current_dt = strtotime("now"); 


The current timestamp is available as constant TIMENOW - seems unnecessary overhead to create it again.