将字符串传递给sprintf语法

Question

I am just trying to pass a date into sql as a DATE (XXXX-XX-XX format), but I can't seem to get sprintf to accept my string date-components. I seem to be following the documentation correctly. using php5.5

$year = ($_POST['year']);
$month = ($_POST['month']); 
$day = ($_POST['day']);

var_dump shows:

 string(4) "1991" string(1) "8" string(1) "5"

however both of these var_dumps are empty:

$dobexpanded =sprintf("%04s-%02s-%02s", $year, $month, $day);
$dateofbirth = (STR_TO_DATE('$dobexpanded', '%Y-%m-%d'));
var_dump($dobexpanded);
var_dump($dateofbirth);

Answer 1

Try with -

$dobexpanded =sprintf("%04d-%02d-%02d", $year, $month, $day);
$dateofbirth = date('Y-m-d', strtotime($dobexpanded));
var_dump($dobexpanded);
var_dump($dateofbirth);