public static function categoryParentSingleSelectEdit($categories, $parent_id, $category_id) {

        // STEP 1: Initiatize the html select tag
        $html = "";
        $html .=  '<select name="parent_id" id="parent_id" size="6" class="form-control">';

        $html .= '<option ';

        if ( $parent_id == 0) {
            $html .= ' selected="selected" ';
        }

        $html .= 'value="';
        $html .= 0;
        $html .= '">';
        $html .= 'No Parent Category';
        $html .= '</option>"';

        // STEP 2: Construct the <option></option> categories for ALL categories in the categories table
        foreach ($categories as $category) {

            if ($category->id == $category_id) {
                continue;
            }

            // If this tag is attached to the post, then SELECTED it
            $selected = "";

            if ( $category->id == $parent_id ) {
                $selected = ' selected="selected" ';
            } 

            $html .= '<option ';
            $html .= $selected;
            $html .= 'value="';
            $html .= $category->id;
            $html .= '">';
            $html .= $category->title;
            $html .= '</option>"';
        }
        $html .= '</select>';

        $html .= self::renderBootstrapMultiselectPlugin(count($categories));

        return $html;
    }