DATE_FORMAT()返回字符串，而不是日期.将3个字符串参数传递给BETWEEN ...谁知道该返回什么.

DATE_FORMAT() returns a string, not a date. Passing 3 string arguments to BETWEEN... who knows what that is going to return.

要取消向后退代码，请使用:

To un-ass-backwards your code, use:

$week_start = date('Y-m-d',time()+( 1 - date('w'))*24*3600);  
$week_end =  date('Y-m-d',time()+( 7 - date('w'))*24*3600); 

以mySQL期望的方式格式化日期，并且:

to format your dates in the way mySQL expects, and:

WHERE 
  start_date BETWEEN '".$week_start."' AND '".$week_end."'

在查询中.

或者，如果您更喜欢面向对象的方法，请执行以下操作:

Or if you would prefer an object-oriented approach, do something like this:

$week_start = new DateTime; 
$week_end = new DateTime;
$week_start->setTimestamp(time()+( 1 - date('w'))*24*3600)); 
$week_end->setTimestamp(time()+( 7 - date('w'))*24*3600);

然后在您的查询中执行

WHERE 
  start_date 
      BETWEEN '".$week_start->format('Y-m-d')."'
      AND '".$week_end->format('Y-m-d')."'

然后，对于其他所有内容，您都可以按照自己的意愿来回显该格式:

Then for everything else, you can echo the format how you wish:

echo $date->format('d-m-Y'); // etc