The more intensive and complicated the business logic, the more you should
lean toward the Java solution.

Execution times tend to be dominated by database interactions. The
PHP/JSP layer generally isn't a significant factor in response time.

http://delsquared.blogspot.com

I studied this for some time. It seems the servlet solution does best in
very heavy traffic situations. In the lightest traffic situations, there is
no difference, in fact, my own experience suggests that in the lighter
traffic situations, (vague defiinition, I know) php is considerably faster.
Additionally, php can be used to pass blobs, and other complex data
structures. Typically, I wil use a servlet for database interaction, but, if
that pukes, have it switch seamlessly over to a php incarnation of the same
thing. Works like a charm, -Ike