Is anything struts/spring can do that php cannot or very hard to
do?
PHP is a technology that can be used in different ways. Similar
to JSP and servlet technology.
Struts is a specific framework using a specific style of
web app.
You can find similar frameworks for PHP, but they are not
nearly as popular in the PHP world as they are in the Java
world.
Frameworks like Struts are very good for large solutions where
you really need structure. They are overly complex for
small solutions.
Today you should consider JSF instead of Struts.
Arne