获取本周一和上周末
echo date('Y-m-d w', strtotime('this week'));//本周一
echo '<hr/>';
echo date('Y-m-d w', strtotime('last day this week'));//上周末
echo date('Y-m-d w', strtotime('this week'));//本周一
echo '<hr/>';
echo date('Y-m-d w', strtotime('last day this week'));//上周末