OrderAnalysis::sortDocumentsByDate

static function sortDocumentsByDate($doc1, $doc2)
{
	$date1 = $doc1->getField($doc1 instanceof Payment ? 'DATE_PAID' : 'DATE_INSERT');
	$date2 = $doc2->getField($doc2 instanceof Payment ? 'DATE_PAID' : 'DATE_INSERT');
	return $date1 > $date2 ? 1 : -1;
}