debuggable

Premature optimization is the root of all evil! That is also true for PHP applications!

Some people say that it is better to defer tuning until after the coding is complete. This advice only makes sense if your programming team's coding is of a high quality to begin with, and you already have a good feel of the performance parameters of your application. Otherwise you are exposing yourselves to the risk of having to rewrite substantial portions of your code after testing.

My advice is that before you design a software application, you should do some basic benchmarks on the hardware and software to get a feel for the maximum performance you might be able to achieve. Then as you design and code the application, keep the desired performance parameters in mind, because at every step of the way there will be tradeoffs between performance, availability, security and flexibility.

Also choose good test data. If your database is expected to hold 100,000 records, avoid testing with only a 100 record database – you will regret it. This once happened to one of the programmers in my company; we did not detect the slow code until much later, causing a lot of wasted time as we had to rewrite a lot of code that worked but did not scale.

Make sure you use profilers to measure the bottlenecks of your application.