float is not enough precision on 32bit CPU

If it is true, some of my code leads to bugs. Could you guide me on what platforms PHP uses single precision? Maybe ARM32?

The https://github.com/php/php-src/blob/master/Zend/zend_float.h tries hard to force double precisioin on any known platform. It's hardly possible to compile modern PHP with single precision floats. Or have I missed something?

zend_float.h tries hard to force double precision on any known platform

Oh, that's something I have missed, thanks for pointing at this! We can then simplify things a bit you're right. We just need to be sure to never use any intermediary int in the process and all should be good. Can you do it in this PR?

Can you do it in this PR?

OK

Well, the default "precision" ini setting is 14. So it's a bit tricky convertion:

$m = 2.0**53/1e6;
printf('format: %.6F, auto: '. $m, $m);
// format: 9007199254.740992, auto: 9007199254.741

The sprintf is slow, but it is the only way to bypass the "precision" setting.

And the maximum date without losing any presition will be "2112-09-17 23:53:47.370496":

php > var_dump(new DateTime(sprintf('@%.6F', 2.0**52/1e6)));
object(DateTime)#1 (3) {
  ["date"]=>
  string(26) "2112-09-17 23:53:47.370496"
  ["timezone_type"]=>
  int(1)
  ["timezone"]=>
  string(6) "+00:00"
}

It's possible to increase it up to "2255-06-05 23:47:34.740992" (plus 1 bit), but code will be less clear:

    public function sleep(float|int $seconds): void
    {
        $microseconds = (float) $this->now->format('Uu') + $seconds * 1e6;
        $datetime = substr_replace(sprintf('@%07.0F', $microseconds), '.', -6, 0);
        $timezone = $this->now->getTimezone();

        $this->now = (new \DateTimeImmutable($datetime, $timezone))->setTimezone($timezone);
    }

Shouldn't we keep the current code then if it doesn't have these issues?

Shouldn't we keep the current code then if it doesn't have these issues?

🤷‍♂️

Dates after 2100 year don't look practical. Anyway, it's a mock for testing only.

Thank you @upyx.