Custom WP_Query not returning results when querying custom post type

Question

I've created a custom post type called 'award':

function award_post_type() {

    $labels = array(
        'name' => 'Awards',
        'singular_name' => 'Award'
    );
    $args = array(
        'labels' => $labels, 
        'public' => true,
        'has_archive' => true,
        'supports' => array( 'title', 'editor', 'excerpt' )
    );
    register_post_type( 'award', $args );

}

add_action( 'init', 'award_post_type' );

Now I am in the award post type's page archive, and I'm trying to display a list of awards ordered by the awards' deadlines (which are stored in a custom field). Next posts should be loaded via AJAX at the click of a 'Load More' button.

First thing I did was alter the main query using pre_get_posts:

function order_by_deadline( $query ) {
    if ( ! is_admin() && is_post_type_archive( 'award' ) ) {
        if( $query->is_main_query() ) {
            $query->set( 'orderby', 'deadline' );
            $query->set( 'meta_key', 'deadline' );
        }
    }
}

add_action( 'pre_get_posts', 'order_by_deadline' );

This works okay. But when I try to load the next posts using AJAX, no results are shown. Here's the action I pass to the AJAX call, which includes the custom WP_Query I've created to call the new posts:

function load_next_awards() { 

    // The number of the page is received from an attribute of the Load More button. I'm 100% sure this has nothing to do with the issues I'm having, so just ignore it.
    $page = $_POST[ 'page' ]; 

    $args = array(
        'paged' => $page, 
        'post_type' => 'award',
        'post_status' => 'publish'
        'post__not_in' => get_option( 'sticky_posts' ),
        'orderby' => 'meta_value_num',
        'meta_key' => 'deadline'
    );

    $next_posts = new WP_Query( $args );  

    if( $next_posts->have_posts() ) :   
        while( $next_posts->have_posts() ) : the_post(); 
            get_template_part( 'views/post/content', get_post_format() );
        endwhile;
    endif;

    wp_reset_postdata();

    die();

} 

I'm at a loss of ideas. The custom WP_Query looks correct to me, but it returns no results when I click on 'Load More'. If I change the post_typeparameter to post or page instead, it does correctly show my posts and pages.

Answer 1

I've found the solution. The problem was I had a different number set for the posts_per_page parameter in the initial query and in the custom query I make via AJAX. In the code I provided posts_per_page is not even there because I'm using a few nested classes, so I've posted a stripped-down version of the code for simplicity. I was sure the issues was with custom post types, never thought using different posts_per_page could cause a problem. Apologies about that.

So yeah, if you're running into the same problem make sure that your posts_per_page is the same for all your queries!

Answer 2

Try initializing the post with $next_posts->the_post() instead of just the_post(). the_post by itself will try to use the main query and in this context there isn't one.

Answer 3

If you are using AJAX, you gotta control your output to "spit" the context only once. And whenever you use a template part or any other functions that print content, it will probably output several times (either by using echo, _e or even HTML markup).

In cases like this you must use the output buffer. Basically, you will put all your content in this buffer instead of printing it and after all processing, you finally outputs/prints it.

Here you can find good reference of using it and [here the PHP manual page] about it 2.

Your functions would be something like this:

function load_next_awards() { 

    // The number of the page is received from an attribute of the Load More button. I'm 100% sure this has nothing to do with the issues I'm having, so just ignore it.
    $page = $_POST[ 'page' ]; 

    $args = array(
        'paged' => $page, 
        'post_type' => array( 'award' ),
        'post_status' => 'publish'
        'post__not_in' => get_option( 'sticky_posts' ),
        'orderby' => 'meta_value_num',
        'meta_key' => 'deadline'
    );

    $next_posts = new WP_Query( $args );  

    if( $next_posts->have_posts() ) :   
        //initiates output buffer
        ob_start();
        while( $next_posts->have_posts() ) : $next_posts->the_post(); 
            get_template_part( 'views/post/content', get_post_format() );
        endwhile;

        // clean outbut buffer (ob) after assigning it's contents to a variable
        $html = ob_get_clean();
    endif;

    wp_reset_postdata();

    // echo cached html markup and leave function
    echo $html;

    die();

} 

Let me know if it helps.