on the other hand, warnings should be killed anyway....

so I am not sure if it is worthy to do this...

@laruence: My main use for this is testing. To test file cache, you need to run something like

    sapi/cli/php run-tests.php -P -c php.ini -d opcache.file_cache=/tmp Zend/
    sapi/cli/php run-tests.php -P -c php.ini -d opcache.file_cache=/tmp -d opcache.validate_timestamps=0 Zend/

However, this causes a lot of test failures even if every thing works "correctly", due to differences in warnings.

Unless by killing warnings you mean that we have plans to remove them from PHP entirely, I think it makes sense to implement this.

I mean that if there is warning, people(php users) should fix it in there own codes...

anyway, I understand your point, maybe just disable opcache while test warnings?

I was concern that we need pay some costs, like performance reduce to achieve this... like save_cwd...

if it cost little, then I have no problems....

If there is a performance concern, I'd be fine with having this behind an ini flag like opcache.replay_warnings=1.

When testing our project on PHP 7.4 I noticed the curly braces deprecation appears only on 1st page load. I'm guessing this is the same thing as this bug report... are there plans to fix this or will it stay as is?

Yes, that's the same problem. I expect this will get fixed eventually, but nobody is actively working on it :)

Implemented in https://github.com/php/php-src/commit/0a74da385dd1cf25cf7870fdc82cbe1c7256fab3 behind a default disabled opcache.record_warnings setting.