Please check the below working code,
for($i=0;$i < $numberDays ; $i++)
{
if ($i != 0)
$start = date('Y-m-d', strtotime("+1 day", strtotime($start)));
$timestamp = strtotime($start);
$day = date("d", $timestamp);
$columns[] = array('name'=>date("d", $timestamp), 'header'=>date("d", $timestamp), 'value' =>'getVal($data,"'.$day.'") > 0 ? CHtml::link(getVal($data,"'.$day.'")," ",array("class"=>"drillDay","id"=>"'.$start.'")) : getVal($data,"'.$day.'")', 'type' => 'raw');
//$columns[] = date("d", $timestamp);
//$datatemp[$start] = $start;
}