Hi Paamayim,
For signals, you need to know which widget it belongs to. For example, 'button-press-event' belongs to GtkWidget. If you go to the page:
http://gtk.php.net/manual/en/gtk.gtkwidget.php
You will see it listed there (you have to scroll all the way to the bottom.)
If you do not know which widget a signal belongs to, you might want to download a copy of the PHP-GTK Explorer which I've written:
http://www.kksou.com/php-gtk2/Tools/PHP-GTK-Explorer.php
Click the 'signal' tab first and search for 'clicked', you will see the result as shown below:
Regards,
/kksou