Dispatch customized events

For a project using amfphp, I am having asynchronism issues. It’s a website/photos gallery, so I get photo datas (from the database) and load the matching thumbnails. But I can’t know when image loadings will be over or which of them will be the last.

I can give a ‘reference’ from parent to child class, or listen loadings in child class from parent, but in this instance, there is a ‘cleaner’ way to do that : to create customized events.