[Magento] Google SEO-friendly Layered Navigation

It is already known, that Magento's SEO is not amazing. That's the reason why I do some pieces of code to make it better:) Here is an another solution, which allows Magento have different titles and descriptions (metadata) in the category sub-pages while layered navigation is in use. By default, there's no matter how many times we will pass filtering by products attributes - metadata will always remain the same and this is one of the common reason for Google to consider these pages as a duplicate content;)

Just put in the following code into the file:

app/code/local/Mage/Page/Block/Html/Head.php

While using this method, all the active filters names and values of current navigation layer are passed to the variable $layerFilters. In addition, this method supports such values as the sort and pagination variables.

    public $layerFilters;
    public $currentFilters;
    public $orderBy;
    public $currentPage;
    public function getLayersMeta(){

        $this->layerFilters = '';
        $state_block = $this->getLayout()->createBlock("catalog/layer_state");
        $this->currentFilters = $state_block->getActiveFilters();

        if(!empty($this->currentFilters)) {
            foreach($this->currentFilters as $filter) {

                $this->layerFilters .= ($this->layerFilters!='') ? ', '.$filter->getName() : $filter->getName();

                $attribute = Mage::getModel('eav/config')->getAttribute('catalog_product', $filter->getFilter()->getRequestVar());
                foreach($attribute->getSource()->getAllOptions(true, true) as $option) {
                    if($filter->getValue() == $option['value']) {
                        $this->layerFilters .= ' - '.strtr($option['label'],array('"'=>"''"));
                    }
                }
            }
            $this->layerFilters = ($this->layerFilters!='') ? $this->__('Shopping by: ').$this->layerFilters.' - ' : '';
        }

        $this->orderBy = '';

        if($this->getRequest()->getParam('order') && $this->getRequest()->getParam('dir')) {
            $this->orderBy .= $this->__('Sort by ').$this->__(htmlspecialchars($this->getRequest()->getParam('order')));
            $this->orderBy .= (htmlspecialchars($this->getRequest()->getParam('dir')) == 'asc') ? ', '.$this->__('ascending') : ', '.$this->__('descending');
        }

        if($this->getRequest()->getParam('limit') && is_numeric($this->getRequest()->getParam('limit'))) {
            $this->orderBy .= (($this->orderBy!='') ? ', ' : $this->__('show')).' '.$this->getRequest()->getParam('limit').' '.$this->__('per page');
        }
        
        if($this->getRequest()->getParam('p') && is_numeric($this->getRequest()->getParam('p'))) {
            $this->currentPage = $this->__('Page').' '.$this->getRequest()->getParam('p').' - ';
        }

        $this->orderBy = ($this->orderBy!='') ? $this->orderBy.' - ' : '';

        return $this->layerFilters.$this->orderBy.$this->currentPage;
    }

Next step will by slight modification of two methods in the same file (getDescription() oraz getTitle()) in this way:

public function getDescription()
    {
        if (empty($this->_data['description'])) {
            $this->_data['description'] = Mage::getStoreConfig('design/head/default_description');
        }
        return $this->getLayersMeta().$this->_data['description'];
    }

    public function getTitle()
    {
        if (empty($this->_data['title'])) {
            $this->_data['title'] = $this->getDefaultTitle();
        }
        return $this->getLayersMeta().htmlspecialchars(html_entity_decode(trim($this->_data['title']), ENT_QUOTES, 'UTF-8'));
    }

Thankfully, we got absolutely unique metadata in category products list according to layer and sorting filters. Example of usage this modification can be found in an online bike shop 123bikes.eu ie. in category mountain bikes.

There is no problem to use this code to generate random content in a category page (like in 123bikes.eu between category images and product list). That's another unique content for Google :)

Let the Magento SEO power grows up! :)