503 Error: Service Unavailable after switching to PHP 8

If I switch on PHP 8, themy e-shop get the 503 Error: Service Unavailable. The server is temporarily busy, try again later!
It happens with any browser (clean cache).
If I switch to PHP version 7.4 the 503 issue no longer occurs and my LT website run right.

https://frontpageserver.it/litecart/
LT 2.4.3
MySQL Version 10.3.25-MariaDB

This happened to our web host as well this last week. It sounds like a distributed PHP update bug that rolled out on cPanel. Try again in two weeks.

This problem is not related to LiteCart. If you are on 2.4.x it's compatible with PHP 8.1.

Did any errors get logged in logs/errors.log?

I have checked immediately but the errors.log is clean; no indication of error by LT.

I have reported your comment about the possible PHP malfunction on the cPanel to Rochen (my web provider).

After your indication Rochen has loaded PHP 8.1.9 and the problem was solved! 
Thanks Tim for your precise technical indication!

Happy to hear that. I just got a report from Australia where this happened as well. Seems to be global.

Yes, my hosting company decided to upgrade me to version 8 which caused the same issue, Tim gave me advice to roll back to previous version and this fixed the problem, thanks Tim!

Please note that the bug reappeared after my provider Rochen (over cPanel) has updated PHP to version 8.1.10. 
As long as the previous version 8.1.9 was running the problem was solved. 
Evidently the PHP 8.0 bug that caused this problem has been reintroduced in this version 8.1.10. 

I am speechless.

Is there any report what the actual big is?

The error log file is quite full. I'm attaching it here.
I tried with PHP v8.0/v8.1 and found same error when saving the litecart article, with PHP v7.4 it is working fine.

[quote]Warning: Undefined constant MYSQLI_OPT_INT_AND_FLOAT_NATIVE[/quote]
This is related to an prehistoric mysql driver enabled for PHP almost as old as the dinosaurs. Use the native driver.
https://www.litecart.net/forums/topic?topic_id=16713

This is however not the cause of the HTTP 500 issue.

I cleaned the error.log from the old warnings to be able to identify new error warnings. 
But there aren't any; When generating the error page: "503 Error: Service Unavailable" no log is generated.

Following your advice I checked PHP and set it up correctly; I will send you the current screenshot.

The error persists with PHP 8.1 while I can only save articles when I revert to PHP 7.4.

[quote]The error persists with PHP 8.1[/quote]
Do you mean the HTTP 503 error, or the MYSQLI warning?

[quote]"503 Error: Service Unavailable" no log is generated[/quote]
No 503 should not produce any php application errors as the application never ran due to a failure in the server.

I mean that the error page "503 Error: Service Unavailable" while I save articles, remain also with the correct PHP 8.1 settings.

No error log is generated from LT during this event.

I can only save articles when I revert to PHP 7.4.

Only when you save them you say?
LOL, LT is that for LitecarT ?

You are entitled to create a support ticket. Click here to begin.

This is done by saving any settings. 
I have also found that after several attempts, most recently trying to clear the system cache (settings->advanced->Clear System Cache), the Litecart WebSite stops responding and only shows this error page.
In order to make my online shop appear again, I am forced to go back to PHP 7.4!

The demo runs PHP 8.1, can you reproduce the problem?
https://demo.litecart.net/

Your demo has no problem!

Please note that the bug reappeared after my provider updated PHP to version 8.1.10. As long as the previous version 8.1.9 was running the 503 issue was solved. Evidently the old PHP 8.0 bug that caused this problem has been reintroduced in this version 8.1.10.
[b]What's the PHP 8.1 version on your server?[/b]

I initially thought about something wrong with my custom template. But then, when the problem also occurs in parts of the setting that do not depend on the template, I'm convinced that there is something in the PHP settings.

I am attaching again the settings I currently have. Do you see anything that could create this service limitation to PHP? I really don't know what else to think.

Your PHP config looks good.

The demo is on PHP 8.1.10 but different servers can use different compilations of the same versions. I think ours is compiled and distributed by CloudLinux.

HTTP 503 errors and no application errors in the log indicates something on the server is broken. You might have some indication of errors logged by Apache in cPanel -> Apache Error Log.

This is something your webhost needs to resolve. You can't do it, apart from swapping to a php version not having this issue.

My provider finally figured out what's causing this 503 error message! Here's what he shared with me.
[quote]I have been able to reproduce the problem and found that the 'acpu' extension is in conflict with your script, so I disabled it via the 'Select PHP Version' page in cPanel.[/quote]
Litecart is now working again and I can save without getting the 503 error window. Now it is again possible to save the settings.
Do you have any idea if this extension is required for LC? The site seems to run correctly without this ACPU extension.

The demo is running the apcu extension without any issues.
Is it possible they can give you a little more information what the actual problem is?
If it was within the application we should have gotten errors logged.

Here the answer from Jeremy R.:
[quote]Sure thing! We had run a system trace against the PHP process being spawned by your website when trying to save changes and noted the following output:

93987 15:52:27 writev(2, [{iov_base="lsphp:/public_html/litecart/storebackend/index.php", iov_len=50}, {iov_base=": ", iov_len=2}, {iov_base="symbol lookup error", iov_len=19}, {iov_base=": ", iov_len=2}, {iov_base="/opt/alt/php81/usr/lib64/php/modules/apcu.so", iov_len=44}, {iov_base=": ", iov_len=2}, {iov_base="undefined symbol: pcre2_match_data_create_from_pattern_8", iov_len=56}, {iov_base="", iov_len=0}, {iov_base="", iov_len=0}, {iov_base="\n", iov_len=1}], 10) = 176
93987 15:52:27 exit_group(127) = ?
93987 15:52:27 +++ exited with 127 +++
92860 15:52:27 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=93987, si_uid=1010, si_status=127, si_utime=5, si_stime=8}

If this is working properly for Tim, then it may indicate a bug in the CloudLinux RPM for PHP 8.1.10 specifically and the pcre2 version it is compiled against.

I can open a ticket with CloudLinux to investigate further, but would it be alright if I share the credentials you provided with them so they can replicate the issue? Note they may also need to re-enable 'apcu' temporarily on your account during testing to confirm the problem.

Jeremy R.[/quote]

Thanks, yeah it looks like something is not right inside that compiled apcu module.
It's optional so you can roll without it.

Thanks Tim for your reassurance. I have also reported your thanks to my provider and closed the corresponding ticket. I hope this clarification will help your LC development!

I hope this clarification will help your LC development!

Let me be clear, this is not a malfunction in LiteCart.

You are absolutely right Tim. I have never written anything else. This is a PHP development error that affects the cPanel interface, as I suspected from the very beginning of this problem (both my provider and yours). However, I am not present on the development forums, nor do I report to the PHP team. I hope some of you, software developers or server system engineers and web service providers, can report this malfunction. As you've already assured me, I don't use this option, but I can imagine who uses it and what problems they might run into. I haven't been in the programming world for decades, but in my day we've always tried to coordinate and work together, knowing that one mistake could affect everyone as a malfunction. That's all. I've already been told by my provider that they have reported the issue to the cPanel and PHP teams. I hope its enough.

Thank you fritz, that should be enough. Await the next php version and see if it's any better.