Exceeding max_file_uploads causes an apparently unrelated "cannot modify headers" warning before script execution

(NOTE: I have edited the test code, it was missing a [] at the end of the name of the file input, which was present in my tests and it's crucial to triggering the issue).

The issue is being suspended because we assume that you are no longer experiencing the problem.

That's a pretty wild assumption, and no, that is not the case. I am still experiencing the problem.

I'll attach phpinfo below.

session.auto_start enabled?

No.

Do you have any extensions installed?

Several.

Error handlers?

I don't think so. Is there a way for an error handler to somehow be there without me registering one in the code (which as you can see I am not doing)?

Is output buffering enabled?

I don't think so, not entirely sure. Phpinfo shows "no value" for output_buffering and output_handler.

On pages that work, any response headers besides the ones that PHP itself creates?

When I do a GET request to the above test script, which doesn't trigger the error, I get these headers in the response:

Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8
Date: Wed, 22 Mar 2023 11:49:26 GMT
Keep-Alive: timeout=1, max=150
Server: Apache
Transfer-Encoding: chunked

When I do a POST request with less than (or up to) 20 files which does not trigger the error, I get the exact same headers. And when I do a POST request with more than 20 files, triggering the error, I get the exact same headers, too.

Works for me in 8.1

When you say "works for me", do you mean you get the expected warning about exceeding the allowed number of uploads, but don't get the warning about failing to set headers? If that is the case, then it works for you. If you are not getting any warning at all, it does not mean it "works for you", you are just not meeting the test case. Note there was a missing [] at the end of the name of the file input in my code (now corrected). Also in order to reproducte you need to have:

display_errors=1
display_startup_errors=1
error_reporting=24567

(some lesser value of error_reporting may be enough).

Here's the output of phpinfo():

Do you have any extensions installed?

Several.

That was a very helpful answer 100

I attached the output of phinfo, from which you should be able to tell which extensions I have.

Do you still have problems if you disable all non-standard extensions? Notably newrelic?

Hmmmm, I can't (reasonably easily) test that without affecting other production websites on the same server.

I have tried on another unrelated server with PHP 7.4 where I don't have the New Relic extension, and indeed it doesn't reproduce the issue. It's a slightly different version of PHP with a completely different set of installed extensions, though, so this doesn't necessarily narrow the issue down to New Relic. It is one suspect, though. I'll see if I can try disabling specific features.

Here's the phpinfo() of this other server not reproducing the issue:

php / php-src

Exceeding max_file_uploads causes an apparently unrelated "cannot modify headers" warning before script execution #10654

Description

PHP Version

Operating System