The admin pages listing the site’s posts and pages come with various text columns (title, tags, categories, author and so on). In order to see what the featured images are, you have to visit each post or page individually. What I will show here, is how to get add a column with a reasonably sized thumbnail copy of the featured image. Please note that this only works for themes that support featured images.
Add a new image size
First we add a new image size. Full details for this function are found on the WordPress add_image_size() codex page.
add_image_size( 'admin-list-thumb', 100, 100, false );
If your theme already has a 100 x 100 image size, you can skip this step. If not, then you may end up with an image size that messes up the layout of the columns.
Add featured image column
Next up, we add the featured image column to the posts and pages list view and pull in the featured image itself using our newly defined image size.
// Dummy up theme support.
//add_theme_support( 'post-thumbnails' );
// Add the posts and pages columns filter. They can both use the same function.
add_filter('manage_posts_columns', 'tcb_add_post_thumbnail_column', 5);
add_filter('manage_pages_columns', 'tcb_add_post_thumbnail_column', 5);
// Add the column
function tcb_add_post_thumbnail_column($cols){
$cols['tcb_post_thumb'] = __('Featured');
return $cols;
}
// Hook into the posts an pages column managing. Sharing function callback again.
add_action('manage_posts_custom_column', 'tcb_display_post_thumbnail_column', 5, 2);
add_action('manage_pages_custom_column', 'tcb_display_post_thumbnail_column', 5, 2);
// Grab featured-thumbnail size post thumbnail and display it.
function tcb_display_post_thumbnail_column($col, $id){
switch($col){
case 'tcb_post_thumb':
if( function_exists('the_post_thumbnail') )
echo the_post_thumbnail( 'admin-list-thumb' );
else
echo 'Not supported in theme';
break;
}
}
Just copy code above to your functions.php and here the preview of result.
