date add one day php

$start_date = "2015/03/02";  
$date = strtotime($start_date);
$date = strtotime("+7 day", $date);
echo date('Y/m/d', $date);

$date = new DateTime('2000-01-01');
$date->add(new DateInterval('P1D'));

$date = date('Y-m-d', strtotime("+1 day"));