Magento native captcha for contact form

Native CAPTCHA settings

First of all find Customer Configuration and open CAPTCHA settings

How to add new form to CAPTCHA settings?

Create new module and add this lines to config.xml:

<?xml version="1.0"?>
<config>
  ...
  <global>
    <events>
      <controller_action_predispatch_routename_controller_method>
        <observers>
          <module>
            <class>module/observer</class>
            <method>checkCaptcha</method>
          </module>
        </observers>
      </controller_action_predispatch_routename_controller_method>
    </events>
  </global>
  <default>
    <captcha>
      <frontend>
        <areas>
          <contact_form>
            <label>Contact Form</label>
          </contact_form>
        </areas>
      </frontend>
    </captcha>
    <customer>
      <captcha>
        <always_for>
          <contact_form>1</contact_form>
        </always_for>
      </captcha>
    </customer>
  </default>
</config>

 You might found here module/observer. It is explained further.

How to show CAPTCHA in contacts form?

Find your form template and insert:

<form action="<?php echo $this->getFormAction(); ?>" id="contactForm" method="post" class="form">
...
<?php echo $this->getChildHtml('captcha'); ?>
...
</form>

 After that find layout xml for your page, for example mine was contacts.xml:

<layout version="0.1.0">
    <contacts_index_index translate="label">
        <label>Contact Us Form</label>
        <reference name="root">
            <action method="setTemplate"><template>page/3columns.phtml</template></action>
            <action method="setHeaderTitle" translate="title" module="contacts"><title>Contact Us</title></action>
        </reference>
        <reference name="content">
            <block type="core/template" name="contactForm" template="contacts/form.phtml">
                <block type="captcha/captcha" name="captcha">
                    <reference name="head">
                        <action method="addJs"><file>mage/captcha.js</file></action>
                    </reference>
                    <action method="setFormId"><formId>contact_form</formId></action>
                    <action method="setImgWidth"><width>230</width></action>
                    <action method="setImgHeight"><width>50</width></action>
                </block>
            </block>
        </reference>
    </contacts_index_index>
</layout>

 

How to check CAPTCHA?

Create Observer for your module:

<?php
class Your_Module_Model_Observer
{
    /**
     * Get Captcha String
     *
     * @param Varien_Object $request
     * @param string $formId
     * @return string
     */
    protected function _getCaptchaString($request, $formId)
    {
        $captchaParams = $request->getPost(Mage_Captcha_Helper_Data::INPUT_NAME_FIELD_VALUE);
        return $captchaParams[$formId];
    }
 
    /**
     * Break the execution in case of incorrect CAPTCHA
     *
     * @param Varien_Event_Observer $observer
     * @return Your_Module_Model_Observer
     */
    public function checkCaptcha($observer)
    {
        $formId = 'contact_form';
        $captchaModel = Mage::helper('captcha')->getCaptcha($formId);
        if ($captchaModel->isRequired()) {
            $controller = $observer->getControllerAction();
            if (!$captchaModel->isCorrect($this->_getCaptchaString($controller->getRequest(), $formId))) {
                Mage::getSingleton('customer/session')->addError(Mage::helper('captcha')->__('Incorrect CAPTCHA.'));
                $controller->setFlag('', Mage_Core_Controller_Varien_Action::FLAG_NO_DISPATCH, true);
                Mage::getSingleton('customer/session')->setCustomerFormData($controller->getRequest()->getPost());
                $controller->getResponse()->setRedirect(Mage::getUrl('*/*/index'));
            }
        }
 
        return $this;
    }
}