计算某天对应当周星期天函数

function get_sun($my_day){//计算某天对应当周星期天函数echo get_sun('2007-06-21');
$myday=explode("-",$my_day);
$year=$myday[0];
$month=$myday[1];
$day=$myday[2];
$week=date("w",mktime(0, 0, 0, $month, $day, $year));
$date_str=date("Y-m-d",mktime(0, 0, 0, $month, $day, $year)-($week*24*60*60));
return $date_str;
}