..->update(
    array("_id" => $idob),
    array(
       '$inc'      => array($type => (int) 1),
       '$addToSet' => array("x"   => (int) $user_id)
    )
);

..->update(
    array("_id" => $idob),
    array(
       '$inc'      => array($type => (int) 1),
       '$addToSet' => array("x"   => (int) $user_id)
    )
);

update(
    array('_id' => $idob, 'x' => array('$nin' => array($user_id))),
    array(
        '$inc' => array($type => 1),
        '$push' => array('x' => (int)$user_id)
    )
)