I am using pre_get_posts() to allow all posts to be displayed on any category archive. This is because I will provide a javascript sorting and filtering method using isotope.js. Any category page will output all posts, but any that aren't a part of that category will initially be hidden.

function show_all_cats( $query ) {
    if ( !$query->is_main_query() ){
        return;
    }
    if ( is_admin() ){
        return;
    }
    if ( $query->is_archive ) {
        $query->set('cat', ''); //here is the problem
        var_dump($query);
        return;
    }
    return;
}
add_action( 'pre_get_posts', 'show_all_cats' );

I have tried setting 'cat' to 0, null, '' and '-' . $currentcategoryid. They all either display only posts that would be displayed otherwise (all in category) or none.

I tried using query_posts() which also didn't work. I was also told:

manipulating taxonomies might require re-running meta queries processing.

I am using pre_get_posts() to allow all posts to be displayed on any category archive. This is because I will provide a javascript sorting and filtering method using isotope.js. Any category page will output all posts, but any that aren't a part of that category will initially be hidden.

function show_all_cats( $query ) {
    if ( !$query->is_main_query() ){
        return;
    }
    if ( is_admin() ){
        return;
    }
    if ( $query->is_archive ) {
        $query->set('cat', ''); //here is the problem
        var_dump($query);
        return;
    }
    return;
}
add_action( 'pre_get_posts', 'show_all_cats' );

I have tried setting 'cat' to 0, null, '' and '-' . $currentcategoryid. They all either display only posts that would be displayed otherwise (all in category) or none.

I tried using query_posts() which also didn't work. I was also told:

manipulating taxonomies might require re-running meta queries processing.

• wp-query
• taxonomy
• archives
• pre-get-posts

4 Answers 4

Just unsetting the cat variable probably isn't enough. The pre_get_posts hook happens after the query variables have already been parsed. So there's probably a tax_query with the taxonomy = category and the terms = your category.

You're already dumping the $query in your code, presumably for debugging. So, look at what you're actually dumping. Do you see the tax_query? Change your code to adjust that $query to have what you want it to have.

Have you tried this?

unset( $query->query_vars['cat'] );

You can use a filter pre_get_posts() to modify SQL query WHERE part:

add_filter( 'posts_where', function ( $where ) {
    $where = preg_replace("regex pattern", "", $where);
        return $where;
    }, 10, 2 );

It is a bit hacking solution but should work.

It is about 4 years later, but if anyone needs the answer, this is the solution:

if ( $query->is_archive ) {
    $q->set( 'category_name', '*your-category-slug*' );
}

Cheers