WP_Query condition affects posts_per_page count

You can try to fetch posts, that don’t have a featured image, with:

$ppp = 5; // posts per page

/**
 * Fetch $ppp posts, without thumbnails, in a given category:
 */
$args = array(
    'cat'            => 1,
    'posts_per_page' => $ppp,
    'meta_query' => array(
        array(
            'key'     => '_thumbnail_id',
            'compare' => 'NOT EXISTS',
        ),
    ),
);
$myposts = get_posts( $args );

But what if there are not enough posts, without a featured image, in that category? Well, then we can just fill the rest with posts with a featured image:

/**
 * Fetch $ppp-x posts in a given category, with thumbnails, if x > 0:
 */
if( $count = count( $posts ) < $ppp ) 
{  
    $args = array(
        'cat'            => 1,
        'posts_per_page' => $ppp - $count,
        'meta_query' => array(
            array(
                'key'     => '_thumbnail_id',
                'compare' => 'EXISTS',
            ),
        ),
    );
    $myposts = array_merge( $posts, get_posts( $args ) );
}

Then you can setup your loop with:

global $post;
foreach( $myposts as $post ) 
{
    setup_postdata( $post );
    ?><li><a href="https://wordpress.stackexchange.com/questions/173313/<?php the_permalink(); ?>"><?php the_title(); ?></a></li><?php
}
wp_reset_postdata();

You might also want to make a check if you got enough posts within the corresponding category.

Notice that this is untested, but I hope you can modify this to your needs.

ps: If I remember correctly, @kaiser already solved something similar in the general case, with some extra flavors added 😉

I will add a link if I find it.

Update: Found it here, I think. There are some interesting answers over there.

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