php get week range

PHP_week_functions.php

<?php
function weekrange($year, $i = 0)
	{
	$week = sprintf("%02d", $i);
	$dto = new DateTime();
	$dto->setISODate($year, $week);
	$year2 = $dto->format('Y');
	if ($year2 < $year) $st = '01-';
	  else $st = $dto->format('d') . "-";
	$dto->modify('+6 days');
	$year2 = $dto->format('Y');
	if ($year2 < $year)
		{
		++$i;
		return weekrange($year, $i);
		}

	$st.= $dto->format('d/m');
	$week = array();
	$week[] = $st;
	$dto->modify('+1 days');
	while ($i < 54)
		{
		$st = $dto->format('d') . "-";
		if ($dto->format('Y') > $year) break;

		$dto->modify('+6 days');
		if ($dto->format('Y') > $year)
			{
			$st.= '31/12';
			$week[] = $st;
			break;
			}
		  else
			{
			$st.= $dto->format('d/m');
			$dto->modify('+1 days');
			$week[] = $st;
			}

		++$i;
		}

	return $week;
	}

$range = weekrange(2018);
echo "<pre>";
print_r($range);
echo "</pre>";
?>