WP_Query – Accessing MetaValue from Query Result

The WP_Query() only queries posts from the wp_posts table. Even if you add additional parameters such as:

'meta_query' => array( 
    array( 
        'key'     => '_thumbnail_id'
        'compare' => 'EXISTS'
    )
)

It looks at the wp_postmeta table to ensure that the posts it pulls has the post_meta _thumbnail_id but it does not also pull the post meta. The query only pulls post data from the wp_posts table. WordPress has a ton of useful functions to get ahold of this information though:

• the_post_thumbnail() pulls and displays the post thumbnail in an <img/> tag.
• get_the_post_thumbnail() – Still pulls the post thumbnail in an <img/> tag but does not display it. Allows you to store it into a variable for later use.

To achieve what you’re trying to do we first have to get the ID of the post-thumbnail, then get the URL:

$thumb_id        = get_post_thumbnail_id();
$thumb_url_array = wp_get_attachment_image_src( $thumb_id, 'medium', true );
$thumb_url       = $thumb_url_array[0];

You can switch out medium with whatever size you need for the post thumbnail.

• Quick Reference ( CSS Tricks )

Alternatively, you could use get_post_meta() to get the thumbnail ID ( or any other post meta values ):

$thumb_id        = get_post_meta( $post->ID, '_thumbnail_id', true );
$thumb_url_array = wp_get_attachment_image_src( $thumb_id, 'medium', true );
$thumb_url       = $thumb_url_array[0];