WordPress设置默认第一张图为特色图

function wpforce_featured() {
global $post;
$already_has_thumb = has_post_thumbnail($post->ID);
if (!$already_has_thumb) {$attached_image = get_children( "post_parent=$post->ID&post_type=attachment&post_mime_type=image&numberposts=1");
if ($attached_image) {foreach ($attached_image as $attachment_id => $attachment) {set_post_thumbnail($post->ID, $attachment_id);
}
}
}
} //end function
add_action('the_post', 'wpforce_featured');
add_action('save_post', 'wpforce_featured');
add_action('draft_to_publish', 'wpforce_featured');
add_action('new_to_publish', 'wpforce_featured');
add_action('pending_to_publish', 'wpforce_featured');
add_action('future_to_publish', 'wpforce_featured');