checking available date

function val_md_day($col,$val,$row, $instanceName)
{
    // Delete image file if it already existed
    $query = "select md_day from ess where md_day = :md_day";
    $queryParams = array('md_day' => $val);
    $stmt = $this->Editor->doQuery($query,$queryParams);
    if($row = $stmt->fetch(PDO::FETCH_ASSOC))
    {
        $not_found = 1;
        $n = 1;
        $check_date = $val;

        while($not_found)
        {
            $check_date = date('Y-m-d', strtotime('-1 day', strtotime($check_date)));
            $query1 = "SELECT md_day FROM ess WHERE md_day = :md_day ";
            $queryParams1 = array('md_day' =>  $check_date);
            $stmt1 = $this->Editor->doQuery($query1,$queryParams1);

            if($row1 = $stmt1->fetch(PDO::FETCH_ASSOC))
            {
                $not_found = 1;
            }
            else
            {
                $not_found = 0;
                $this->Editor->showDefaultValidationMsg = false;
                $this->Editor->addTooltipMsg('Available Date is : ' . $check_date );
                return false;
            }
        }
    }
    else
    {
      return true;
    }
}