JSON阿贾克斯PHP MySQL的

I have table users.

• id
• login
• password

I want to display the data in JSON format through php mysql

page: config.php

$rep = $db->query("SELECT * FROM users");
$array_user = array();
while($data =  $rep->fetch()){
    $array_user = $data;
}
echo json_encode($array_user);
?>

page listUsers.php

<div  id="tab"></div>

<script>
    $(document).on("ready",function(){

        loadData();
    });
    var loadData = function(){
        $.ajax({
            type:"POST",
             url:"config.php"
        }).done(function(data){
            console.log(data);
            var users = JSON.parse(data);


            for(var i in users){
                $("#tab").append(users[i].login + "<br>");
            }

        });
    }
</script>

but it appears to me "undefined".