// deleting the user record should be sufficient due to ON DELETE CASCADE foreign key references
// but not all database backends actually support this so let's do it by hand
foreach (array('identities','contacts','contactgroups','dictionaries','cache','cache_index','cache_messages','cache_thread','searches','users') as $table){
foreach (array('identities','contacts','contactgroups','dictionary','cache','cache_index','cache_messages','cache_thread','searches','users') as $table){
$db->query('DELETE FROM ' . $db->table_name($table, true) . ' WHERE `user_id` = ?', $user->ID);