If $datetime value is `null`, empty string, or whitespace(s), it will default to the current datetime or 'now'.
<?php
$date = null; // or '' or '     '
var_dump(date_create($date));
?>
returns
<?php
object(DateTime)#1 (3) {
  ["date"]=>
  string(26) "2025-07-29 00:59:02.992777"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(3) "UTC"
}
?>