New Post Notifications for Users – BUDDYPRESS

Like JItendra Rana already mentioned, you just send a notification to the author. If all users should get a notification, you must loop through all your users and add a notification to everyone. You get the users with get_users. Here is the modified code to realize it:

function bp_post_published_notification( $post_id, $post ) {
    $author_id = $post->post_author; /* Post author ID. */
    $users = get_users();

    /* Loop all users */
    foreach( $users as $user ) {
        if ( bp_is_active( 'notifications' ) ) {
            bp_notifications_add_notification( array(
                'user_id'           => $user->ID,
                'item_id'           => $post_id,
                'component_name'    => 'custom',
                'component_action'  => 'custom_action',
                'date_notified'     => bp_core_current_time(),
                'is_new'            => 1,
            ) );
        }
    }
}
add_action( 'publish_post', 'bp_post_published_notification', 99, 2 );