Environment::set() is slow

[fedeisas]

Hi!

In our app we (ab)use Environment::set() when bootstrapping to set all of our site's configuration. We set some defaults, and then depending on our environment (prod/test/dev) we overwrite some of those.

I was just trying to improve my app's performance and I've found that Environment::set() uses Set::merge() which is kinda slow.

Sometimes you want to set some configuration overwriting the existing values. Perhaps I'm misusing this class.

Example:

<?php
// This is slow
Environment::set(true, ['assets' => $foo + Environment::get('assets')]);

// This is fast
$bar = $foo + Environment::get('assets');
Environment::set(true, ['assets' => null]);
Environment::set(true, ['assets' => $bar]);

[mariuswilms]

Initial set has been minimally optimized in 1e7b327. Set::merge seems already pretty optimized, but maybe someone might want to give it a try. @fedeisas Benchmarks showing the differences (and where time is spent) between the two cases outlined in your report would help.