Sometimes we want to dynamically generate the post title of a custom post type from data entered in other fields, without the user seeing the title in the editing screen.

Update CPT Post Title from post data

add_action( 'save_post', 'set_cpt_post_title' );

function set_cpt_post_title( $post_id, $post ) {

		// Don't change title for revisions.
		if ( wp_is_post_revision( $post_id ) ) {
			return;
		}

		// Get the current post type.
		$post_type = get_post_type( $post );

		// If this isn't a 'MY_POST_TYPE_KEY' post, don't update the title.
		if ( 'MY_POST_TYPE_KEY' !== $post_type ) {
			return;
		}

		// Get the data here.


		// Create the title.
		$title = '';

		// Unhook this function so we don't loop indefinitely.
		remove_action( 'save_post', array( $this, 'set_cpt_post_title' ) );

		// Update our title.
		wp_update_post( array(
			'ID'         => $post_id,
			'post_title' => $title,
		) );

		// Re-hook this function, since we are done.
		add_action( 'save_post', array( $this, 'set_cpt_post_title' ) );

	}