FoxyShop: Customize Product Details Box

//Code to Allow Featured Product Checkbox or Other Special Custom Fields in Product Details
//Place this in your functions.php file
//Edit the field names and descriptions in the first function
//Then put your field names in the array in the second function

//Show New Field in Admin
add_action('foxyshop_admin_product_details','my_custom_product_details');
function my_custom_product_details($post_id) {

        //Checkbox Example
        $fieldname = "_is_featured"; //has to start with _
        $fieldescription = "Featured Product";
        ?>
        <div style="clear:both"></div>
        <div class="foxyshop_field_control">
                <input type="checkbox" name="<?php echo $fieldname; ?>" id="<?php echo $fieldname; ?>" style="float: left; margin: 5px 0 0 10px;"<?php echo checked(get_post_meta($post_id, $fieldname, 1),"on"); ?> />
                <label style="width: 210px; margin-top: 4px;" for="<?php echo $fieldname; ?>"><?php echo htmlspecialchars($fieldescription); ?></label>
        </div>
        <div style="clear:both"></div>
        <?php


        //Text Entry Example
        $fieldname = "_special_price"; //has to start with _
        $fieldescription = "Special Price";
        ?>
        <div style="clear:both"></div>
        <div class="foxyshop_field_control">
                <label for="<?php echo $fieldname; ?>"><?php echo htmlspecialchars($fieldescription); ?></label>
                <input type="text" name="<?php echo $fieldname; ?>" id="<?php echo $fieldname; ?>" value="<?php echo htmlspecialchars(get_post_meta($post_id, $fieldname, 1)); ?>" />
        </div>
        <div style="clear:both"></div>
        <?php


}

//Save New Field
add_action('foxyshop_save_product','my_save_custom_product_details');
function my_save_custom_product_details($post_id) {

        //Enter All of Your Field Names in an array
        $fieldnames = array('_is_featured', '_special_price');

        foreach ($fieldnames as $fieldname) {
                $fieldvalue = isset($_POST[$fieldname]) ? $_POST[$fieldname] : '';
                foxyshop_save_meta_data($fieldname, $fieldvalue);
        }

        return $post_id;
}