function activeuser(userId) {
  $.post("/admin/activate_user", {
      userid: userId
  }, function (response) {
  });
}

<span id="enable<?=$user->id; ?>" class="cb-enable <?=$active_class;?>" onclick="return activeuser(<?= $user->id ?>);"><span>Active</span></span>
   <span id="disenable<?=$user->id; ?>" class="cb-disable <?=$deactive_class;?>" onclick="return deactiveuser(<?= $user->id ?>);"><span>De-active</span></span>

if($('#thatSpan').hasClass('cb-enable') && $('#thatSpan').hasClass('selected'))
{
  //your code goes here.
}

if($('#thatSpan').is('.cb-enable.selected'))
{
  //your code goes here.
}

function activeuser(userId){
    if(! ($(this).hasClass('cb-enable') && $(this).hasClass('selected')) ){
        $.post("/admin/activate_user",
            {
            userid: userId
            },
            function(response){
                if(response == "active"){
                    $('#enable'+userId).addClass('selected');
                    $('#disenable'+userId).removeClass('selected');
                    $('#disenable'+userId).addClass('pointer');
                    $('#enable'+userId).removeClass('pointer');
            }
         });
    }
}