<?
$days_to_add = 7;
$date = strtotime("01/01/1969");
$newdate = mktime(0,0,0,date("m",$date),date("d",$date)+$days_to_add,date("Y",$date));
echo date("m/d/Y", $newdate);
// or...
$date = strtotime("01/01/1969");
$newdate = $date + ($days_to_add * 24 * 60 * 60);
echo date("m/d/Y", $newdate);
?>