【转】php周转日期，查询周的起始日期

1. function getWeekDate($year,$weeknum){  
2.     $firstdayofyear=mktime(0,0,0,1,1,$year);  
3.     $firstweekday=date('N',$firstdayofyear);  
4.     $firstweenum=date('W',$firstdayofyear);  
5.     if($firstweenum==1){  
6.         $day=(1-($firstweekday-1))+7*($weeknum-1);  
7.         $startdate=date('Y-m-d',mktime(0,0,0,1,$day,$year));  
8.         $enddate=date('Y-m-d',mktime(0,0,0,1,$day+6,$year));  
9.     }else{  
10.         $day=(9-$firstweekday)+7*($weeknum-1);  
11.         $startdate=date('Y-m-d',mktime(0,0,0,1,$day,$year));  
12.         $enddate=date('Y-m-d',mktime(0,0,0,1,$day+6,$year));  
13.     }  
14.       
15.     return array($startdate,$enddate);      
16. }