Magento block in before_body_end with form_key being cached

Question

Magento block in before_body_end with form_key being cached

We use a block for login form data in the block before_body_end. Only since some time we have seen this block is cached and the form_key has a mismatch when wew submit it to Magento.

question: how can we (really) prevent the block below from being cached?

<catalog_category_default>
    <reference name="before_body_end">
    <block type="core/template" name="autologin" as="autologin">
        <action method="setTemplate" ifconfig="webmyneautologin/webmyneautologin_group/category"><template>autologin/autologin.phtml</template></action>
        <action method="setCacheLifetime" />
    </block>
    </reference>
</catalog_category_default>

Answer 1

try adding below code

<catalog_category_default>
    <reference name="before_body_end">
    <block type="core/template" name="autologin" as="autologin">
        <action method="setTemplate" ifconfig="webmyneautologin/webmyneautologin_group/category"><template>autologin/autologin.phtml</template></action>

        <action method="unsetData"><key>cache_lifetime</key></action>
        <action method="unsetData"><key>cache_tags</key></action>
    </block>
    </reference>
</catalog_category_default>

Answer 2

Depends what you want to do. We use block caching for almost all our blocks. So what we do is replace the Magento Form key with example: "$$FORMKEY$$" and than CACHE IT !

Then the onlything you need is to replace this with the REAL formkey just before sending back to client.

  <frontend>
    <events>
      <controller_front_send_response_before>
        <observers>
          <gn_blockcache>
            <type>singleton</type>
            <class>gn_blockcache/observer</class>
            <method>controllerFrontSendResponseBefore</method>
          </gn_blockcache>
        </observers>
      </controller_front_send_response_before>
    </events>
  </frontend>

This is the replace code:

    /**
     * Fix form_key in html coming from cache
     *
     * @param Varien_Event_Observer $observer
     *
     * @return boolean
     */
    public function controllerFrontSendResponseBefore($observer) {
        /** @var Zend_Controller_Response_Http $response */
        /** @noinspection PhpUndefinedMethodInspection */
        $response = $observer->getFront()->getResponse();
        $headers  = $response->getHeaders();
        $isHtml   = true; // Because it's default in PHP
        foreach ($headers as $header) {
            if ('Content-Type' == $header['name'] && false === strpos($header['value'], 'text/html')) {
                $isHtml = false;
                break;
            }
        }
        if ($isHtml) {
            $html = $response->getBody();

            /** @noinspection PhpUndefinedMethodInspection */
            $newFormKey      = Mage::getSingleton('core/session')->getFormKey();
            $templateFormkey = '$$FORMKEY$$';
            $html            = str_replace($templateFormkey, $newFormKey, $html);
            $response->setBody($html);
        }

        return true;
    }

You can also do this on the "afterToHtml()" of the block it selfs, but we have decided for a generic sollution that works for all blocks with "$$FORMKEY$$".

How to inject the $$FORMKEY$$ constant (cart example):

class Gn_BlockCache_Helper_Cart extends Mage_Checkout_Helper_Cart {

    /** @var Gn_BlockCache_Helper_Data */
    protected $helper;

    public function __construct() {
        $this->helper = Mage::helper('gn_blockcache');
    }

    /**
     * Add to url: /form_key/$$FORMKEY$$/   <== Will be replace on "controller_front_send_response_before"
     *
     * @param Mage_Catalog_Model_Product $product
     * @param array                      $additional
     *
     * @return string
     */
    public function getAddUrl($product, $additional = array()) {
        if ($this->helper->getEnabledCartFormkey()) {
            return parent::getAddUrl($product, array_merge([Mage_Core_Model_Url::FORM_KEY => '$$FORMKEY$$'], $additional));
        } else {
            return parent::getAddUrl($product, $additional);
        }
    }
}