Use binary format for state set cache for better performance and OPcache exclusion

[Toflar]

I want to disable storing the state set in OPcache by default for the reasons described in the docs of this PR.

However, the current solution using ini_set('opcache.enable', '0'); won't work because this affects all other scripts loaded after the state_set.php as well. However, I couldn't find a way to disable OPcache for just one specific file while still dumping that file as pure PHP because that's still a lot faster than loading all the states from SQLite...

Any hints welcome 😊

Using pack() and unpack() was way faster in my tests than just a regular PHP array so let's drop OPcache support completely for better interoperability.

[ausi]

Did you try storing it in binary format using something like

$states = [1 => true, 7 => true, 123 => true];
file_put_contents(…, pack('N*', ...array_keys($states)));

And then loading it back in using unpack:

$data = unpack('N*', file_get_contents(…));
$states = array_combine($data, array_fill(0, \count($data), true));

Depending on alphabet size and index length you might need a larger or smaller integer. N is unsigned 32 bit.

[Toflar]

I thought about it but did not do any measurements because I thought this for sure will be slower than just a regular PHP array. But to my own surprise this was not the case but quite the opposite, it's actually way, way faster! 🤯
So I've dropped all OPcache stuff and what we're left with is a problem solved and better performance introduced 🤣 Nice!