jquery ui autocomplete with database

Question

I fairly new to JQuery and perhaps trying to achieve something that might be abit harder for a beginner. However I am trying to create an autocomplete that sends the current value to a PHP script and then returns the necessary values.

Here is my Javascript code

$("#login_name").autocomplete({
    source: function(request, response) {
 $.ajax({
     url: "http://www.myhost.com/myscript.php",
     dataType: "jsonp",

     success: function(data) {
  alert(data);
  response($.map(data, function(item) {
      return {
   label: item.user_login_name,
   value: item.user_id
      }
  }))
     }
 })
    },
    minLength: 2
});

And here is the the last half of "myscript.php"

while($row = $Database->fetch(MYSQLI_ASSOC))
{
    foreach($row as $column=>$val) 
    {
        $results[$i][$column] = $val;
    }
    $i++;
}
print json_encode($results);

Which produces the following output

[{"user_id":"2","user_login_name":"Name1"},{"user_id":"3","user_login_name":"Name2"},{"user_id":"4","user_login_name":"Name3"},{"user_id":"5","user_login_name":"Name4"},{"user_id":"6","user_login_name":"Name5"},{"user_id":"7","user_login_name":"Name6"}]

Can anyone tell me where I am going wrong please? Starting to get quite frustrated. The input box just turns "white" and no options are shown. The code does work if I specify an array of values.

UPDATE I have changed the code to and still having no luck.

$("#login_name").autocomplete({
    source: "/ajax/login_name.php",
    dataType: "json",
    minLength: 2,
    cache: false,
    select: function(event, ui) {
        alert(ui);
    }
});

Using FireFox's Web Developer tool, I am getting an error "b is null".

Answer 1

Finally found the solution that fits my needs

$("#login_name").autocomplete({
  source: function(request, response){
    $.post("/ajax/login_name.php", {data:request.term}, function(data){     
        response($.map(data, function(item) {
        return {
            label: item.user_login_name,
            value: item.user_id
        }
        }))
    }, "json");
  },
  minLength: 2,
  dataType: "json",
  cache: false,
  focus: function(event, ui) {
    return false;
  },
  select: function(event, ui) {
    this.value = ui.item.label;
    /* Do something with user_id */
    return false;
  }
});