bebeboutik/modules/expresscart/expresscart.php

<?php
class ExpressCart extends Module {
	public function __construct() {
		$this->name = 'expresscart';
		$this->tab = 'front_office_features';
		$this->version = '1.0';

        parent::__construct();

        $this->displayName = $this->l('Express Cart');
        $this->description = $this->l('Adds a quick add-to-cart feature to the product list.');
    }

    public function install() {
		if(!parent::install()
		OR !$this->registerHook('header')) {
			return FALSE;
		}

		return TRUE;
	}

    public function hookHeader() {
        global $smarty;
        $page_name = $smarty->getTemplateVars('page_name');

        if($id_category = Tools::getValue('id_category')) {
            $smarty->assign('id_category', $id_category);
            return $this->display(__FILE__, 'header.tpl');
        }

        if($page_name == 'product') {
            return $this->display(__FILE__, 'header2.tpl');
        }
	}
}