Merged two WP_Queries, posts per page and pagination not working

Question

I merged two WP_Queries with the code below, it has pagination setup as well as posts per page in the final combined object but those settings aren't working. My page shows 24 posts, where is it getting this number from and why isn't pagination working?

$args1 = array(
    'post_type' => 'post',
    'posts_per_page' => -1
    );
$query1 = new WP_Query( $args1 );

    $args2 = array(
    'post_type' => 'product',
    'product_tag' => 'home',
    'posts_per_page' => -1
    );
$query2 = new WP_Query( $args2 );

$paged = get_query_var('paged') ? get_query_var('paged') : 1;

$finalargs = array(
  'paged' => $paged,
  'posts_per_page' => 3
);

$wp_query = new WP_Query($finalargs);

$wp_query->posts = array_merge( $query1->posts, $query2->posts );

$wp_query->post_count = count( $wp_query->posts );

echo '<pre>';
//var_dump($wp_query); exit(0);
echo '</pre>';

The output of var_dump is below, so if my wp_query has posts per page and pagination setup why isn't it working?

object(WP_Query)#566 (47) {
  ["query"]=>
  array(2) {
    ["paged"]=>
    int(1)
    ["posts_per_page"]=>
    int(3)
  }
  ["query_vars"]=>
  array(61) {
    ["paged"]=>
    int(1)
    ["posts_per_page"]=>
    int(3)
    ["error"]=>
    string(0) ""
    ["m"]=>
    string(0) ""
    ["p"]=>

Answer 1

I had this exact problem. I just stumbled upon the solution!

In case this helps you, in both my initial queries before the array merge I changed the posts_per_page to be -1 like 'posts_per_page' => -1 instead of 10. When I did this, the pagination links suddenly appeared and worked fine.

I then added 'posts_per_page' => 10 to my final query after the array_merge for it to show 10 per page.

EDIT:

Now looking at your code I see you did that too. Then you should maybe change the way you query as I did, by merging your results array and then doing a query on the merged results. It worked for me and your way did not.

$other_reviews = get_posts( 
    array( 
        'fields'         => 'ids',
        'post_type'      => 'post', 
        'cat'            => 36, 
        'posts_per_page' => -1, 
        'paged'          => $paged, 
        'orderby'        => 'date', 
        'order'          => 'DESC' 
    )
);

$reviews = get_posts( 
    array( 
        'fields'         => 'ids', 
        'post_type'      => array( 'reviews1','review2' ), 
        'posts_per_page' => -1, 
        'paged'          => $paged, 
        'orderby'        => 'date', 
        'order'          => 'DESC' 
    )
);

Then we merge them together:

// merging ids
$post_ids = array_merge( $other_reviews, $reviews );

and construct the combined query with:

// the main query
$query = new WP_Query(
    array(
        'post_type'      => 'any',
        'post__in'       => $post_ids, 
        'paged'          => $paged,
        'orderby'        => 'date', 
        'order'          => 'DESC',
        'posts_per_page' => 10
    )
);