Get posts from multiple post type

Question

I need to display posts from multiple post type with two queries so I found this answer: How to display posts from multiple post type in random order in wordpress?

But can't use it to get post data like post content or post title, The author of the answer write I must set up by setup_postdata but I can't understand.

Any help, please?

Answer 1

So you want to query posts from multiple post types, but also with different query-arguments like custom field, tax_query or categories.

As you did not post what you tried, have already or want to have, please try something like this:

We are using 3 queries to set everything up. You can add different arguments to each query.

Get post ID´s from our first post type, product:

$first_post_ids = get_posts( array(
    'fields'         => 'ids', // only return post ID´s
    'posts_per_page' => '5',
    'post_type'      => array('product'),
));

Get post ID´s from our second post type, post:

$second_post_ids = get_posts( array(
    'fields'         => 'ids', // only return post ID´s
    'posts_per_page' => '5',
    'post_type'      => array('post'),
));

Merge our two queries into one:

$merged_post_ids = array_merge( $first_post_ids, $second_post_ids);

Build the third query:

$wp_query = new WP_Query( array(
    'post_type' => 'any', // any post type
    'post__in'  => $merged_post_ids, // our merged queries
) );

The loop:

if ( $wp_query->have_posts() ) : 
    while ( $wp_query->have_posts() ) : $wp_query->the_post();

        //look at $post here !!
        //Example: $post->post_type;
        //this return the type of each post so you can do checks and stuff

        //for example show title and content
        the_title( '<h2>', '</h2>' );
        the_content();

    endwhile;

    // reset after query
    wp_reset_query();

else :
    echo 'Sorry, no posts matched your criteria.';
endif;

---

Update: Check if array_merge is not null to prevent any types showing

array_merge is used to merge 2 arrays, like the name suggests.

So for example, if $first_post_ids is a string, than it will not work. Thats why we use 'fields' => 'ids', in our queries.
Because as the Codex says:

'ids' - Return an array of post IDs.

And even if one of these two queries is empty (i.e. we have no posts), array_merge will still work.

But yes, we can check array_merge:

//... first two queries

$merged_post_ids = array_merge( $first_post_ids, $second_post_ids );

//check if the array_merge exists/not null
if ( $merged_post_ids ) {

    $wp_query = new WP_Query( array(
        'post_type' => 'any', // any post type
        'post__in'  => $merged_post_ids, // our merged queries
    ) );

    //... your query code here

}//END if $merged_post_ids

You can also expand it with an else statement to let another query run.