<?php
$nextWeek = time() + (7 * 24 * 60 * 60);
// 7 days; 24 hours; 60 mins; 60 secs
echo 'Now: '. date('Y-m-d') ."
";
echo 'Next Week: '. date('Y-m-d', $nextWeek) ."
";
// or using strtotime():
echo 'Next Week: '. date('Y-m-d', strtotime('+1 week')) ."
";
?>