WordPress Featured Images in Post List - Post Types

wp-featured-image-post-types.php

<?php
//Run in init action
//Replace apartments with your post type name
//Must use PHP >= 5.3
add_filter( 'manage_apartments_posts_columns', function( $columns ) {
    $columns['apt_thumb'] = __('Thumb');
	return $columns;
} );

add_action( 'manage_apartments_posts_custom_column', function( $column_name, $post_id ) {
	if( $column_name == 'apt_thumb' ) {
		if ( has_post_thumbnail( $post_id ) ) {
			echo get_the_post_thumbnail( $post_id, 'thumbnail' );
		}
		
	}
}, 10, 2 );