Untitled

Pass variable to function, by value
function GetDateToReturn($StartDate)
{
    $date = $StartDate;
    return $date->modify('+2 day');
}

$FromDate = date_create('1-Feb-2012');
echo ' From : ' . $FromDate->format('Y-m-d); //From : 2012-02-01
$ToDate = $this->GetDateToReturn($FromDate);
echo ' From : ' . $FromDate->format('Y-m-d'); //From : 2012-02-03
echo ' To : ' . $ToDate->format('Y-m-d'); //To : 2012-02-03

$date = clone $StartDate;
return $date->modify('+2 day');