Code Snippet to Automatically Set Featured Image from First Post Image

Solution to Automatically Set Featured Image

Custom Code Solution

Add this code to your theme's functions.php file or in a site-specific plugin. The code scans the post content for the first image when saving a post and sets it as the featured image if no featured image exists.

Here's the main function that handles the automatic featured image setting:

function set_featured_image_from_first_post_image($post_id) {
    // Skip if post already has featured image
    if (has_post_thumbnail($post_id)) {
        return;
    }

    // Get post content
    $post = get_post($post_id);
    $content = $post->post_content;

    // Search for first image in the content
    preg_match_all('/<img[^>]+>/i', $content, $images);

    if (empty($images[0])) {
        return;
    }

    // Get first image src
    preg_match('/src="([^"]+)/i', $images[0][0], $src);
    
    if (empty($src[1])) {
        return;
    }

    // Download and attach image to post
    $upload = media_sideload_image($src[1], $post_id, '', 'id');
    
    if (!is_wp_error($upload)) {
        set_post_thumbnail($post_id, $upload);
    }
}

Add this hook to activate the function:

add_action('save_post', 'set_featured_image_from_first_post_image', 10, 1);

Plugin Solutions

If you prefer a plugin solution, here are reliable options:

1. Auto Featured Image - Simple plugin that sets the first image as featured image
2. Quick Featured Images - More advanced options for bulk management of featured images

Additional Notes

• The code runs when saving/updating a post
• It only sets the featured image if one isn't already set
• Works with both uploaded images and external images
• Handles proper attachment creation in the media library

Remember to:

• Back up your site before adding custom code
• Test the functionality on a staging environment first
• Consider performance impact on sites with many posts