$someVar = 'now';
$uppedDate = new DateTime($someVar);
$diff = $uppedDate->diff(new DateTime());

$mdiff = (int)$diff->format('%m');
$ddiff = (int)$diff->format('%d');
$content = array_filter([$mdiff, $ddiff]);

// if condition is always true
if ($content) {
    die();
}

// the error is gone
if (\count($content) > 0) {
	die();
}

$content = array_filter([$mdiff, $ddiff], fn(): bool => false);
// the error is gone
if ($content) {
	die();
}