Currently using a query_posts() in my theme - want to use a request filter in stead

Question

I am currently using this code in my theme right before showing the content of the custom post type my_post_type:

$title = $post->post_title;
query_posts( array (
    'post_type' => 'page', 
    'posts_per_page' => -1,
    'my_taxonomy' => $title
    ));

This means that when I go to .../my_post_type/some_title, I see all pages that are assigned "some_title" as my_taxonomy.

Now I want to do the same thing in a plugin in stead of a theme. This means is (I guess) that I have to use the "request" filter? I have tried to do this:

add_filter( 'request', 'alter_the_query' );
function alter_the_query( $request ) {
    $request['post_type'] = 'page';
    $request['my_taxonomy'] = 'some_title'; // just hardcoded so far while testing
    $request['posts_per_page'] =  -1;
    return $request;
}

But it doen't return any pages at all. Not even this works:

add_filter( 'request', 'alter_the_query' );
function alter_the_query( $request ) {
    $request['post_type'] = 'page';
    return $request;
}

What am I doing wrong, or how can I achieve the same thing as my with my call to query_posts()?

Thanks a lot!

Answer 1

The code you've provided doesn't actually print out the list of pages; it just creates the query for them. Assuming you have additional code for displaying them, the easiest way to accomplish what you want in a plugin is to build that list, then add them using the_content filter. I would probably create the list of pages in one function, the add those pages to the_content with a second function added to the filter. Here's something that should help to get your started:

function my_posts_list() {
    global $post;

    query_posts( array (
        'post_type' => 'page', 
        'posts_per_page' => -1,
        'my_taxonomy' => $post->post_title
    ));

    // Build your HTML list of posts from the query.
}

function filter_the_content($content) {
    // Only filter the content if we're on a single 'my_post_type' page.
    if (is_singular('my_post_type')) {
        $postsList = my_posts_list();
        $content = $postsList . $content;
    }
    return $content;
}

add_filter('the_content', 'filter_the_content');

There are, of course, plenty of additional things you could do with this, like check if there the list of posts isn't empty.

Answer 2

WordPress provides a great hook, pre_get_posts for exactly what I think you're trying to do.

Here's what your code would probably look like

add_action( 'pre_get_posts', 'alter_the_query' );
function alter_the_query() {
    if( is_main_query() && get_post_type() == 'my_post_type' ) {
        global $post;
        $title = $post->post_title;
        $query->set('post_type', 'page');
        $query->set('posts_per_page', -1);
        $query->set('my_taxonomy', $title);
    }
}

Nacin and others are recommending that pre_get_posts replace the use of query_posts() anyway, so hopefully this works for you and sends you in the right direction.