Question

I have setup BuddyPress with a custom profile field that lists check boxes for tags related to my site.

Is there a way to send automatic notifications to registered BuddyPress users based on their custom profile field selection whenever a new post goes up?

Answer 1

The save_post hook can help you out.

http://codex.wordpress.org/Plugin_API/Action_Reference/save_post

Something along the lines of:

function send_bp_message( $post_id ) 
{
  //verify post is not a revision
  if( wp_is_post_revision($post_id) )
  {
    return;
  }

  // get the user ids you want to notify
  global $bp, $wpdb;

  $custom_field_id = 1; // the profile field you want to check
  $custom_field_value = 'true'; // the value you're looking for

  $stmt = $wpdb->prepare("
    SELECT
      {$bp->profile->table_name_data}.user_id
    FROM
      {$bp->profile->table_name_data}
    LEFT JOIN
      {$bp->profile->table_name_fields} ON {$bp->profile->table_name_fields}.id = {$bp->profile->table_name_data}.field_id
    WHERE
      {$bp->profile->table_name_fields}.id = %d
    AND
      {$bp->profile->table_name_data}.value LIKE %s
  ", $custom_field_id, $custom_field_value);

  $recipient_ids = $wpdb->get_col($stmt); // array of matched user ids

  // send buddypress notification to matched user ids
  // (you could loop through $recipient_ids to send individual notifications)
  $msg_args = array(
    'sender_id' => 1, // 1 = admin
    'recipients' => $recipient_ids,
    'subject' => 'New post',
    'content' => 'A new post has been created...'
  );
  $thread_id = messages_new_message($message_args);        
}
add_action('save_post', 'send_bp_message');