创建帖子时如何自动将特色图片添加到自定义帖子？

Question

I have a custom post called 'project'.
When a user logs in, post is automatically created.
When the post is created, I need to automatically add a featured image (only one image: number 6120) for all posts.
I tried the following code but it doesn't add a featured image.
I'm a beginner so I'm not good at coding, would you please let me know how to solve this problem?

function wpsites_auto_set_featured_image() {
global $post, $post_type;
if( $post_type == "project" ) {
$featured_image_exists = has_post_thumbnail($post->ID);
if (!$featured_image_exists)  {
 $attached_image = get_children( "post_parent=$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, '6120');
wp_reset_query();                                
   }
  }
 }
}
}
add_action('save_post', 'wpsites_auto_set_featured_image');

Thank you.

Answer 1

Use save_post_{$post->post_type} for particular post type. check below code.

function wpsites_auto_set_featured_image( $post_id ) {
    if ( !has_post_thumbnail( $post_id ) )  {
        $thumbnail_id = 6120;
        update_post_meta( $post_id, '_thumbnail_id', $thumbnail_id );
    }
}
add_action( 'save_post_project', 'wpsites_auto_set_featured_image', 10 );