first commit

extension/oc_theme_example/catalog/controller/startup/theme_example.php

@@ -0,0 +1,19 @@
+<?php
+namespace Opencart\Catalog\Controller\Extension\OcThemeExample\Startup;
+class ThemeExample extends \Opencart\System\Engine\Controller {
+	public function index(): void {
+		if ($this->config->get('config_theme') == 'theme_example' && $this->config->get('theme_theme_example_status')) {
+			// Add event via code instead of DB
+			// Could also just set view/common/header/before
+			$this->event->register('view/*/before', new \Opencart\System\Engine\Action('extension/oc_theme_example/startup/theme_example.event'));
+		}
+	}
+
+	public function event(string &$route, array &$args, mixed &$output): void {
+		$override = ['common/header'];
+
+		if (in_array($route, $override)) {
+			$route = 'extension/oc_theme_example/' . $route;
+		}
+	}
+}

extension/oc_theme_example/catalog/view/template/common/header.twig

@@ -0,0 +1 @@
+test header