Callback function for admin mass unblocking users.
function user_user_operations_unblock($accounts) {
$accounts = user_load_multiple($accounts);
foreach ($accounts as $account) {
// Skip unblocking user if they are already unblocked.
if ($account !== FALSE && $account->status == 0) {
$account->status = 1;
$account
->save();
}
}
}