PHP 7.0 is already history. But do you know how to take full advantage of it? If the engine is faster on all operations in general, some of them are particularly optimized. With PHP 5, you may have taken some habits that are no longer topical to write faster code?
I propose to review with you the various optimization techniques implemented in Symfony, which make the v4 the fastest ever published. This will be an opportunity to twist the puzzle around a few preconceived ideas, and give you a few more for the day when you'll try to squeeze the last few milliseconds out of this intensive loop. Benchmark in support of course.