How am I supposed to call a secondary PHP file? Here is my code.
add_filter( \'woocommerce_product_tabs\', \'woo_simfree_product_tab\' ); function woo_simfree_p
You'll need to use get_stylesheet_directory() to include your file, if it's a child theme do something like this:
get_stylesheet_directory()
require get_stylesheet_directory() . "/custom-groups/grouped-simfree.php";
The file should be at wp-content/themes/your-child-theme/custom-groups/grouped-simfree.php