How to extend an email layout in a theme from a module

In this blog, we are about to learn, how to extend an email layout in a theme from a module to add some content to an existing email template.

Usually, we use the provided email theme, and sometimes we would like to add some extra information or change the header/footer/content. One of the advantages of new theme layouts is that PrestaShop uses the Twig template so we can take advantage of its extension and blocks features.

To extend an email layout with HTML content in the existing email template, we need to follow the following steps:

First of all, we need to register a new hook named ‘actionListMailThemes’

We use this hook to extend HTML content in the existing email template.

Now we need to add our layout to the theme’s layout collection.
To do this we use the statement followed by the imported class namespace above the class declaration:

use PrestaShop\PrestaShop\Core\MailTemplate\Layout\Layout;
use PrestaShop\PrestaShop\Core\MailTemplate\ThemeCollectionInterface;

Now we define the definition of hook functionality as Follows:

/**
     * @param array $hookParams
     */
    public function hookActionListMailThemes(array $hookParams)
    {
        if (!isset($hookParams['mailThemes'])) {
            return;
        }

        /** @var ThemeCollectionInterface $themes */
        $themes = $hookParams['mailThemes'];
        $theme = $themes->getByName('classic');
        if (!$theme) {
            return;
        }

        // First parameter is the layout name, second one is the module name (empty value matches the core layouts)
        $orderConfLayout = $theme->getLayouts()->getLayout('order_conf', '');
        if (null === $orderConfLayout) {
            return;
        }

        //The layout collection extends from ArrayCollection so it has more feature than it seems..
        //It allows to REPLACE the existing layout easily
        $orderIndex = $theme->getLayouts()->indexOf($orderConfLayout);
        $theme->getLayouts()->offsetSet($orderIndex, new Layout(
            $orderConfLayout->getName(),
            __DIR__ . '/mails/layouts/order_conf.html.twig',
            ''
        ));
    }

We will get results as follows: