JSP or PHP?

JSP and everything based upon that (Struts, Tiles etc.) meanst that you have to stick with it.

PHP works with Java

It is important to note JSP is just one language with which Java objects can be accessed. PHP also can also integrate with Java, which means that it can be used as the scripting language for activating Java logic, just as much as JSP can. Unlike JSP, however, PHP also integrates with other component models, such as Microsoft's COM, and adding support for new object models is extremely easy. This means PHP's extensibility is infinite. JSP, on the other hand, is completely dependent on Java.

IBM programmer Sam Ruby uses PHP in combination with Java. Using the native Java support in PHP, Java objects can be created and used transparently, as if they were regular PHP objects