jquery autocomplete: works for first value, how to enable it for next?

I'm using autocomplete so user can easly enter data on inputs, like this:

 <?
$a = new etiqueta(0, '');
$b = $a->autocomplete_etiquetas();
?>
<script type="text/javascript">
    function cargar_autocomplete_etiquetas(){
        $("#tags").autocomplete({
            source: [<? echo $b; ?>]
        });
    }
</script>

$a = $b its an array with a result like: 'help','please',i','need','to,'be able to', 'select next item',' with autocomplete';

and i checked the ui documentation, but it doesn't fith with my source method.. any idea? I'm trying like this (edited with Bugai13 aportation):

 <?
$a = new etiqueta(0, '');
$b = $a->autocomplete_etiquetas();
?>
<script type="text/javascript">
    function cargar_autocomplete_etiquetas(){
    $("#tags").autocomplete({
        source: [<? echo $b; ?>],
        multiple: true,
        multipleSeparator: ", ",
        matchContains: true
    });
}

</script>

but i don't know how to do it.. any idea? are .push and .pop functions from the autocomplete? or shall i define, them?

thanks again!

PS: i'm getting adicted to this site! PS: come on dudes, i think the answer will be very usefull for many people PS: is it allowed to offer paypal reward?

I've use following to get work multiple autocomplete for tags with ',' separator, hope this help your:

It's full my code that work. In my case in parse function items it just json array, try to add parse method:

   $("#txtTags").autocomplete(UrlFactory.TAGS_AUTOCOMPLETE_URL, {
    matchContains: true,
    width: 320,
    max: 10,
    highlight: false,
    multiple: true,
    multipleSeparator: ", ",
    scroll: true,
    scrollHeight: 300,
    dataType: "json",
    parse: function (data) {
        var result = Result.fromJson(data);

        var items = result.getJson("Tags");
        var arr;
        if (items != null)
            arr = items.split(",");
        return $.map(arr, function (row, i) {
            return {
                data: row,
                value: row,
                result: row
            }
        });
    },
    onItemSelect: function () {

    },
    formatItem: function (data, i, n, value) {
        if (value != null) {
            value = ltrim(value);
            value = rtrim(value);
        }
        return value;
    }
});

So, you need something like this:

function cargar_autocomplete_etiquetas(){
    $("#tags").autocomplete({
        source: [<? echo $b; ?>],
        multiple: true,
        multipleSeparator: ", ",
        matchContains: true
    });
}

What does echo $b; print? I would expect you would need something like echo implode(',', $b), or even echo '"' . implode('", "', $b) . '"'; to make this work, if $b really is a PHP array.

Edit: (of course I'm only assuming you're using PHP, but if it <?s like PHP and $s like PHP...)