因工作需要，需要获取周四开始一周的开始结束日期，而php没有提供获取本周开始及结束日期的方法，因此写了一个方法方便以后使用。
计算方法：
<?php
/**
* 计算指定日期的一周开始及结束日期
* @param DateTime $date 日期
* @param Int $start 周几作为一周的开始 1-6为周一~周六，0为周日，默认0
* @retrun Array
*/
function getWeekRange($date,$start=0){
// 将日期转时间戳
$dt = new DateTime($date);
$timestamp = $dt->format('U');
// 获取日期是周几
$day = (new DateTime('@'.$timestamp))->format('w');
// 计算开始日期
if($day>=$start){
$startdate_timestamp = mktime(0,date('m',$timestamp),date('d',$timestamp)-($day-$start),date('Y',$timestamp));
}elseif($day<$start){
$startdate_timestamp = mktime(0,$timestamp)-7+$start-$day,$timestamp));
}
// 结束日期=开始日期+6
$enddate_timestamp = mktime(0,$startdate_timestamp),$startdate_timestamp)+6,$startdate_timestamp));
$startdate = (new DateTime('@'.$startdate_timestamp))->format('Y-m-d');
$enddate = (new DateTime('@'.$enddate_timestamp))->format('Y-m-d');
return array($startdate,$enddate);
}
?>
实例：测试分别以周一至周日为开始计算日期的一周开始及结束时间
<?php
$date = '2016-04-27';
for($start=0; $start<=6; $start++){
list($startdate,$enddate) = getWeekRange($date,$start);
echo 'date:'.$date.' week start:'.$start.' range:'.$startdate.','.$enddate.'<br>';
}
?>
输出：
date:2016-04-27 week start:0 range:2016-04-24,2016-04-30
date:2016-04-27 week start:1 range:2016-04-25,2016-05-01
date:2016-04-27 week start:2 range:2016-04-26,2016-05-02
date:2016-04-27 week start:3 range:2016-04-27,2016-05-03
date:2016-04-27 week start:4 range:2016-04-21,2016-04-27
date:2016-04-27 week start:5 range:2016-04-22,2016-04-28
date:2016-04-27 week start:6 range:2016-04-23,2016-04-29
