ChatGPT provided a working solution: function load_custom_header_for_campaign( $template ) { // Check if the ‘campaign’ query var is set if (isset($_GET[‘campaign’])) { // Load the header-lp.php file instead of the default header add_filter(‘get_header’, function($header) { return ‘lp’; // This will load header-lp.php }); } return $template; } add_filter(‘template_include’, ‘load_custom_header_for_campaign’); It notes: The issue you’re encountering … Read more