Add a Custom Column in WordPress Posts and Custom Post Types Admin Screen

This tutorial demonstrates how to add a featured image column to the WordPress posts screen, and extend this functionality to custom post types. Let's streamline the explanation and improve clarity.

Step 1: Enable Featured Images

First, ensure your theme supports featured images. Open your theme's functions.php file (create it if it doesn't exist) and add the following code:

<code class="language-php">add_theme_support( 'post-thumbnails' );
add_image_size( 'featured_preview', 200, 150, false );</code>

This enables featured image support and creates a custom thumbnail size (featured_preview) for previewing images in the new column. The false argument prevents cropping.

(Image: Featured Image setting in the WordPress post editor)

Step 2: Add Featured Image Column to Posts

Next, add a custom column to display the featured image in the WordPress posts list. Add these functions to your functions.php file:

<code class="language-php">function st4_add_featured_image_column( $defaults ) {
    $defaults['featured_image'] = __( 'Featured Image' );
    return $defaults;
}

function st4_show_featured_image_column( $column_name, $post_ID ) {
    if ( $column_name == 'featured_image' ) {
        $featured_image = get_the_post_thumbnail( $post_ID, 'featured_preview' );
        if ( $featured_image ) {
            echo $featured_image;
        } else {
            echo '<img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/174054013775854.jpg" class="lazy" alt="Add a Custom Column in WordPress Posts and Custom Post Types Admin Screen "> <em>(Image: Posts list with new Featured Image column)</em>
<p>You can show/hide this column via the <strong>Screen Options</strong> panel.</p>
<p><img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/174054013887569.jpg" class="lazy" alt="Add a Custom Column in WordPress Posts and Custom Post Types Admin Screen "> <em>(Image: Screen Options panel)</em></p>
<p><strong>Step 3: Extend to Custom Post Types</strong></p>
<p>To add the featured image column to custom post types,  simply replace <code>manage_posts_columns</code> and <code>manage_posts_custom_column</code> with the appropriate custom post type hooks. For example, for a custom post type named "movies":</p>
<pre class="brush:php;toolbar:false"><code class="language-php">add_filter( 'manage_movie_posts_columns', 'st4_add_featured_image_column' );
add_action( 'manage_movie_posts_custom_column', 'st4_show_featured_image_column', 10, 2 );</code>

(Image: Featured image in a Movie post)

(Image: Featured Image column in the Movies custom post type)

Further Considerations (briefly):

• Targeting Specific Post Types: Use the manage_{post_type}_posts_columns and manage_{post_type}_posts_custom_column hooks to add the column to only specific custom post types.
• Multiple Columns: Easily add multiple custom columns by expanding the st4_add_featured_image_column and st4_show_featured_image_column functions.
• Removing Default Columns: Use unset() within the filter to remove default columns.

This revised response provides a more concise and focused explanation, while maintaining the essential information and images. The code is also improved for readability and efficiency.

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