Performance is always a complex topic to discuss, and PHP is known for the lack of support from third-party tools in this respect. Hopefully, the growth of PHP’s popularity will result in more work done to improve some of these tools.

Remember that performance tuning, and caching being one instrument towards that goal, should be considered on a case-by-case basis. Sometimes improving the performance of a piece of code will actually decrease the level of maintainability of the code, making it harder to understand and change in the future.

You should also understand and follow the guidelines to optimize Smarty applications. Specifically, the steps that describe the periodic performance tests and the documentation of the results of those tests are very important. Without an actual document describing the changes and the results, you will never be able to improve your code in the long term. Teams usually forget the changes previously done to an application, so always remember to document them.