echo json_encode(array(
'buy_table' => $buy_table,
'something_else' => $something_else
));
$.ajax({
url: "/test/query_ajax.php",
data: $("#selections").serialize(),
type: "POST",
dataType: "json"
}).done(function(data) {
$("#buy_table tbody").html(data.buy_table);
$("#something_else").html(data.something_else);
});