PHP日期始终返回1970年1月1日而不是null

The date returned part should be null until i updated it

<td width="50" align="center"><?php echo $returneddate; ?></td>

I have changed my date to strtotime but it is executing it to 01-01-1970 everytime. It is supposed to be null until i updated the date. I have googled so many solutions but couldnt get a thing.

Thank you in advance.

check if there is value in database then do date formatting:

$display_date = ($db_date)?date('d-m-y',strtotime($db_date)):'';