My application heavily uses webservices and doesn't use database atall. there is a webservice layer which gets data from database and sends it to php UI. so the phpUI doesn't directly interact with the databases. I want to improve the performance of this application what is a better approach to improve the performance? should I use memcached and cache control headers or is there any other way to implement the caching to improve the performance? I want a way to reduce my Http requests to webservices
since you use the term "webservice" I assume that you are using HTTP as the transport layer. If you are using RESTful architecture for your webservices, all you need is a standard http caching proxy in-between your app and the services.
I suggest you to use a webserver like nginx or lighttpd if possible. They are a magnitude faster and easier to configure.