ProductLink with color attribute in url-friendly

<?php
// Description :  With this modifications, the friendly url link will contains
// the color name if available
// using Prestashop > 1.4.4
class Link extends LinkCore{


    /**
      * Return the correct link for product, with the color name if there
      * is a color attribute available
      *
      * @param mixed $id_product Can be either the object or the ID only
      * @param string $alias Friendly URL (only if $id_OBJ is the object)
      * @return string link
      *
      */
    public function getProductLink($id_product, $alias = NULL, $category = NULL, $ean13 = NULL, $id_lang = NULL)
    {
        $id_lang = (int)$id_lang;
        if (!is_object($id_product))
            $id_product = new Product($id_product);

        $attributs = $id_product->getAttributeCombinaisons($id_lang);
        // adding color attribute, first part
        foreach($attributs AS $k => $attribut)
            if($attributs[$k]['is_color_group'])
            {
                $color = $attribut['attribute_name'];
                break;
            }
        // if link_rewrite
        if ($this->allow == 1)
        {
            $url = _PS_BASE_URL_.__PS_BASE_URI__.$this->getLangLink($id_lang) ;
            if (isset($id_product->category) AND !empty($id_product->category) AND $id_product->category != 'home')
                $url .= $id_product->category.'/';
            $url .= $id_product->id.'-'.$id_product->link_rewrite;
            // adding color attribute, part II
            if (isset($color))
                $url .= '-'.$color;
            $url .= $id_product->ean13 ? '-'.$id_product->ean13 : '';
            $url .= '.html';
        }
        else
            $url = _PS_BASE_URL_.__PS_BASE_URI__.'product.php?id_product='.(int)$id_product->id;

        return $url;
    }
}