Redirect to product's page and have attributes automatically selected

Question

From a controller I redirect to a configurable product's page by

$productUrl = $this->_customSearch();
$url = Mage::getBaseUrl().$productUrl.'.html';
header('Location: '.$url);
die();

The children products can be searched by specific attribute (corresponding to their color group) and I want when the user is redirected to the product page - the attribute "Color" (a drop-down menu) to already have the certain color selected, depending on the searched value.

Now, what I cannot wrap my mind around is how to make the attribute auto-selected when the page loads. In the controller I can get the color of the product from the product object, but what next? I guess I have to deal with Ajax here, but the URL of the product's page has nothing that can give me a hint.

Any ideas?

Answer 1

Magento supports for the configurable product page, the selected options in the url. See this example on demo: http://demo.magentocommerce.com/men/shirts/french-cuff-cotton-twill-oxford-477.html#92=22&180=79

You can specify after # the attribute ids and selected values:

#attr_id1=value1&attr_id2=value2&...

SO if you know the attribute id and the color value you should be able to build your url easily before redirecting to it.

Answer 2

You can add some identifier in the url and use this identifier to change the configurable option at the product page as in the following code

/** see http://www.magentocommerce.com/magento-connect/configurable-preselect-by-amasty.html
*/

var amasty_configurable_pre_select = new Class.create();

amasty_configurable_pre_select.prototype = {
initialize: function()    {},

select: function()
{
    var args = $A(arguments);
    $$('.product-options .super-attribute-select').each(function(select, i){
        if (args[i])
        {
            select.value = args[i];
            spConfig.configureElement(select);
        }
    });
}
};