全局变量与数据库访问，哪一个更好？

Question

I read a lot about how evil global variables are in PHP, but I am trying to optimize a code I am writing. In this webapp a lot of functions are using the same data (about up to 50 items at once) to perform numerous operations and the data itself is stored in a database.

I have two options which are a) fetching data from the database EVERY TIME a function needs it or b) fetching the data ONCE and storing it in (a) global variable(s).

When it comes to performance, which option is the best ?

Answer 1

1. There is nothing wrong with "global variables". It is passing data into functions using global keyword is prohibited (but nevertheless, using this keyword to pass indeed global variable is okay).
2. Yes, speaking of one script instance (and sane amount of data), there is no use for reaching for database for the same data again. Fetch it once and then use in whatever functions you need. It's okay and nothing wrong with it.
3. When it comes to performance, here comes the best option ever:
   • do care of performance only if you have a certain reason to.