Based upon this I have tried to write the following code as:

Custom Page template:

 Template Name: product_filter
    do_action( 'pre_get_posts', 'COOLING');



 function shop_filter_cat($query, $arg) {
    if (!is_admin() && is_post_type_archive( 'product' ) && $query->is_main_query()) {
       $query->set('tax_query', array(
                    array ('taxonomy' => 'product_cat',
                                       'field' => 'slug',
                                        'terms' => $arg

But I have got following warning:

Warning: Missing argument 2 for shop_filter_cat(), called in E:\xampp\htdocs\wordpress\wp-includes\plugin.php on line 600 and defined in E:\xampp\htdocs\wordpress\wp-content\themes\storefront\functions.php on line 56

and error:

Fatal error: Uncaught Error: Call to a member function is_main_query() on string in E:\xampp\htdocs\wordpress\wp-content\plugins\woocommerce\includes\wc-deprecated-functions.php:677 Stack trace: #0 E:\xampp\htdocs\wordpress\wp-includes\plugin.php(524): wc_shop_order_status_backwards_compatibility('COOLING') #1 E:\xampp\htdocs\wordpress\wp-content\themes\storefront\testing.php(6): do_action('pre_get_posts', 'COOLING') #2 E:\xampp\htdocs\wordpress\wp-includes\template-loader.php(75): include('E:\xampp\htdocs...') #3 E:\xampp\htdocs\wordpress\wp-blog-header.php(19): require_once('E:\xampp\htdocs...') #4 E:\xampp\htdocs\wordpress\index.php(17): require('E:\xampp\htdocs...') #5 {main} thrown in E:\xampp\htdocs\wordpress\wp-content\plugins\woocommerce\includes\wc-deprecated-functions.php on line 677

1 Answer 1


you make a mistake in the call of add_action
the last parameters must be changed from 1 to 2

  • 2
    the do_action is probably not needed as well Oct 9, 2016 at 9:28
  • ok, it removed warning and what about error Oct 9, 2016 at 9:36
  • MuhammadMuazzam: I think @MarkKaplun already answered that for you regarding the error, since you're using string as an input argument. There's also no second input argument for pre_get_posts by default.
    – birgire
    Oct 9, 2016 at 10:18
  • do_action is being used to change parameter value when custom page input field value change that I will do as well. so when I have tried to change it as do_action( 'pre_get_posts', '','COOLING'); it still have error Oct 9, 2016 at 10:51
  • @MuhammadMuazzam This is not the way to pass on data to the main query, since you're overriding the query object with a string value (hence the error) and the main query has already been activated when you are inside the template file.
    – birgire
    Oct 9, 2016 at 12:07

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