current date+4 days

This function allows the addition of day(s),month(s),year(s) to the original date while still preserving the Hours, minutes and seconds
You can also modify to add to hours, miuntes and even seconds.
 
<?php
function add_date($givendate,$day=0,$mth=0,$yr=0) {
      $cd = strtotime($givendate);
      $newdate = date('Y-m-d h:i:s', mktime(date('h',$cd),
    date('i',$cd), date('s',$cd), date('m',$cd)+$mth,
    date('d',$cd)+$day, date('Y',$cd)+$yr));
      return $newdate;
              }

?>

how do I call this function

$newdate = add_date(curdate(),4)
echo format($newdate,'m/d/Y');

thanks