Menampilkan Tanggal 15 Bulan yang akan datang

here the answer just i found 15 months mean 1 year 3 months so can split it into 1 for year and 3 for month so, code be like this

<?php date_default_timezone_set('Asia/Jakarta');
$m = 3;
$n = 1;
$nextN = mktime(0, 0, 0, date("m") + $m, date("d"), date("Y") + $n);
echo date('d-m-Y', $nextN);
?>