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;
}