<?php
$year = '2015';
$week = '01';
$month = date('m', strtotime($year . 'W' . $week));
$weeks = [
'0' => ((int)$week == 1) ? date('W', strtotime('December 28th,' . $year - 1)) : (int)$week - 1,
'1' => $week,
'2' => (date('W', strtotime('December 28th,' . $year)) == $week) ? '01' : (int)$week + 1,
'3' => (date('W', strtotime('December 28th,' . $year)) == $week) ? '01' : (int)$week + 2,
'4' => (date('W', strtotime('December 28th,' . $year)) == $week) ? '01' : (int)$week + 3,
'5' => (date('W', strtotime('December 28th,' . $year)) == $week) ? '01' : (int)$week + 4
];
print_r($weeks);
preferences:
44.43 ms | 402 KiB | 5 Q