php獲取一年內所有周數，並顯示開始時間和結束時間

<?
function get_week($year){   
$year_start = $year . "-01-01";  
$year_end = $year . "-12-31";  
$startday = strtotime($year_start); 
if (intval(date('N', $startday)) != '1') {   
$startday = strtotime("next monday", strtotime($year_start)); //獲取年第一週的日期
}  
$year_mondy = date("Y-m-d", $startday); //獲取年第一週的日期
$endday = strtotime($year_end);  
if (intval(date('W', $endday)) == '7') {  
$endday = strtotime("last sunday", strtotime($year_end)); 
}    
//$num = intval(date('W', $endday));可以獲取當年以前的年份有多少周，如果是當年還沒到12-31號$num爲1   
$num = 52;//一年約52周
for ($i = 1; $i <= $num; $i++) {  
$j = $i - 1;     
$start_date = date("Y-m-d", strtotime("$year_mondy $j week ")); 
$end_day = date("Y-m-d", strtotime("$start_date +6 day"));   
$week_array[$i] = array(            $start_date, $end_day);  
}   
return $week_array;
}

print_r(get_week(2020));  

?>