Page.php

<?php

/**
 * Base page type
 */
class Page extends SiteTree
{

    #region Declarations

    /**
     * Additional fields which are available to all pages
     * @var array
     */
    private static $db = [
        'PreviewText' => 'Text'
    ];

    #endregion Declarations

    #region Relationships


    private static $extensions = [
        'ResponsiveImagesExtension'
    ];

    #endregion Relationships

    #region Private Methods

    #endregion Private Methods

    #region Public Methods

    public function getCMSFields()
    {

        $this->beforeUpdateCMSFields(function (FieldList $fields) {

        });

        $fields = parent::getCMSFields();

        $fields->addFieldToTab('Root.Metadata', TextareaField::create('PreviewText'));


        Requirements::customCSS(
            <<<CSS
			.htmleditor label.left {
    			width: 100%;
			}
CSS
        );

        return $fields;
    }

    /**
     * Validation which is applied to all pages
     * @return RequiredFields
     */
    public function getCMSValidator()
    {
        return new RequiredFields(
            []
        );
    }

    /**
     * Set to return true if this page should not show it's children in the nav
     *
     * @return bool
     */
    public function HideChildrenFromNavigation()
    {
        return false;
    }

    /**
     * Set to return false if this page should not be added to as the first child of it's dropdown list if it is a
     * parent
     *
     * @return bool
     */
    public function ShowInDropdownIfParent()
    {
        return true;
    }

    /**
     * Returns the site default meta tags
     * This overload also checks if the domain contains one of our non-indexable domains
     * If it does it adds the noindex meta tag.
     *
     * @param bool $includeTitle
     *
     * @return string
     */
    public function MetaTags($includeTitle = true)
    {
        $tags          = parent::MetaTags($includeTitle);
        $domains       = Config::inst()->get('Development', 'NoIndexDomains');
        $currentDomain = strtolower(Director::protocolAndHost());
        if (is_array($domains) && !empty($domains)) {
            foreach ($domains as $nonIndexableDomain) {
                if (strpos($currentDomain, strtolower($nonIndexableDomain)) !== false) {
                    return $tags . '<meta name="robots" content="noindex">';
                }
            }
        }

        return $tags;
    }

    #endregion Public Methods

}

/**
 * Base page controller
 */
class Page_Controller extends ContentController
{

    #region Declarations

    private static $allowed_actions = [];

    #endregion Declarations

    #region Public Methods

    public function init()
    {
        parent::init();
    }

    public function ActiveIf($link)
    {
        $link = substr($link, -1) === '/' ? substr($link, 0, -1) : $link;
        $link = substr($link, 0, 1) === '/' ? substr($link, 1) : $link;

        return strtolower(Controller::curr()->getRequest()->getURL()) === strtolower($link) ? 'active' : '';
    }

    public function CategoryPages()
    {
        return ProductsPage::get_one(ProductsPage::class)->AllChildren();
    }

    public function ContinueShoppingLink()
    {
        if(ProductsPage::get_one(ProductsPage::class)){
            return ProductsPage::get_one(ProductsPage::class)->Link();
        }
    }

    #endregion Public Methods

}