Populating a drop down list with a combination of PHP and Javascript

I have the following view:

<form action=<?=$target;?> method="post" name="editForm">
    <div id="page1">
        <select id="categories" name="category" onmouseover="populateCategory(<?=$result?>, <?=$id?>)" >
        </select>
    </div>
</form>

which utilizes the following javascript function on the select tag:

function populateCategory(subCategories, id) {

    var select = document.getElementById(id);

    var opt = document.createElement("option");

    opt.text = "--Please make a selection--";

    for (i = 0; i < subCategories.length; i++) {
        var opt = document.createElement("option");

        opt.value = i;
        opt.text = subCategories[i];

        select.add(opt);
    }
}

The arguments passed to the function are the following variables:

 $result = $this->getCategories(0);
$id = 'categories';

which calls the following function

public function getCategories($parent, $published = 1) {

        //Sanitize Params...    

        //$sanParent = $this->db->getEscaped($parent);
        //$sanPublished = $this->db->getEscaped($published);

        $query = 
        "SELECT * FROM #__adsmanager_categories 
        WHERE parent = " . $parent .
        " AND published = " . $published;

        $this->db->setQuery($query);
        $result = $this->db->loadAssocList();

        var_dump($parent);

        if (!$result) {
            return false;
        }

        return $result;

    }

The low-down:

The last function I posted makes a request to a database, obtaining a list of categories which are intended to be used to create a dropdown list. I thought that if I passed the obtained categories to the JavaScript function, that I may be able to populate it the easy way. Am I doing this wrong? I have a feeling it's a JavaScript issue, as the function call doesn't even seem to happen. When I open the browser debugger, for example, there is no indication of whether or not it was called.

update:

Here is the what the html-source lists:

<script type="text/javascript">

function populateCategory(subCategories, id) {



    var select = document.getElementById(id);



    var opt = document.createElement("option");



    opt.text = "--Please make a selection--";



    for (i = 0; i < subCategories.length; i++) {

        var opt = document.createElement("option");



        opt.value = i;

        opt.text = subCategories[i];



        select.add(opt);

    }

}

</script>



<form action=/index.php?option=com_adsmanager&amp;task=write&amp;Itemid=1 method="post" name="editForm">

    <div id="page1">

        <select id="categories" name="category" onmouseover="populateCategory(Array, categories)" >

        </select>

    </div>

</form>