首先使用 createFromFormat 方法，提供输入格式：

Use createFromFormat method first, provide the input format:

$exd = DateTime::createFromFormat('d M, Y', '01 Dec, 2015');
// arguments (<format of the input>, <the input itself>)
$exd = date_format($exd, 'Y-m-d'); // then choose whatever format you like
echo $exd;