[jQuery] modify from server two jquery elements in the same time

[phicarre]

I would like to modify two jquery elements in the same time from PHP
module. The PHP module is called by .ajax

$.ajax(
    {
        type: "POST",
        url:'my_module.php',
        dataType: 'html',
         success: function(resultat) { ***** ????? *****},
        error: function(requete,iderror) {alert(iderror);}
    })
}

<div id=field1>...
<div id=field2>...

PHP code:

echo " ***new value for field1 **** new value for field2 *** "

How to formulate the success function AND the echo instruction ?