[RFC] Display Function Arguments in Errors

Hi,

I believe there is almost never “No Impact” to the ecosystem. In fact
the RFC partly acknowledges it in the “Backward Incompatible Changes”
section. Even if the corresponding sub-vote to default to 1 doesn't
pass, code needs to be prepared for someone to set it to 1 themselves.
This includes off-the-shelf software (such as WordPress, or Drupal, or
whatever).

I have the following two suggestions (that follow pretty naturally, but
are nevertheless an impact that should be spelled out):

a) Custom error handlers (set_error_handlers()) need to be prepared for
the error message format to change. Even though we don't make any
guarantees about error messages themselves, the existing format with
“function name first” is reasonably structured for automated parsing
(e.g. using a regular expression). This also includes error tracking
tools that try to group error messages by function or similar.

b) System administrators have one more INI setting to deal with and need
to make a decision. Previous versions of the RFC template had an
explicit “INI setting” section, but given it's so rare we add new INI
settings these days, it has been removed from the template. For the few
that still add one, properly discussing the consequences still is valuable.

These are all excellent points.

I want to add one more side-effect that feels discounted: PII and other
sensitive data leaking through logs. Partly what the INI setting is
supposed to address, but IMO it only does so on paper.
I have dealt with that issue many times, and developers tend to either not
take it seriously or propose naive patchwork solutions such as blacklisting
patterns in already produced logs. Plus, there's an inherent temptation to
temporarily enable such settings for debugging purposes, not realizing the
act itself represents a data leak and it is permanent. If this is a serious
problem without args values being present today, imagine the amplification
effect from this addition.

With that being said, I also know the pain of having to deal with
borderline useless error messages. The proposal isn't without merit, but
I'd look for alternative approaches that don't create security headaches.

Cheers,
Andrey.

Hi

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.
https://wiki.php.net/rfc/display_error_function_args

Thank you for the RFC. I have the following comments:

I believe there is almost never “No Impact” to the ecosystem. In fact the RFC partly acknowledges it in the “Backward Incompatible Changes” section. Even if the corresponding sub-vote to default to 1 doesn't pass, code needs to be prepared for someone to set it to 1 themselves. This includes off-the-shelf software (such as WordPress, or Drupal, or whatever).

I'm adding this to the ecosystem impact section.

I have the following two suggestions (that follow pretty naturally, but are nevertheless an impact that should be spelled out):

a) Custom error handlers (set_error_handlers()) need to be prepared for the error message format to change. Even though we don't make any guarantees about error messages themselves, the existing format with “function name first” is reasonably structured for automated parsing (e.g. using a regular expression). This also includes error tracking tools that try to group error messages by function or similar.

b) System administrators have one more INI setting to deal with and need to make a decision. Previous versions of the RFC template had an explicit “INI setting” section, but given it's so rare we add new INI settings these days, it has been removed from the template. For the few that still add one, properly discussing the consequences still is valuable.

I do recognize that PHP has been trending towards fewer knobs;
unfortunately, I don't see a better way other than adding a new
knob.

As for the naming of the bikeshed, I suggest error_ignore_args for consistency with zend.exception_ignore_args.

I'm not attached to the name; if others think this sounds good, I'll
adjust the RFC and PR.

For the voting options: You need to define a tie-breaker for the secondary votes.

I might be a little dense here; I see tie-breakers mentioned in
feature-proposals, but I don't see any guidance on how to include them
in an RFC. The other RFCs I've been skimming don't seem to mention them
either.

Best regards
Tim Düsterhus

Hi

Am 2026-03-30 16:40, schrieb Calvin Buckley:

If I don't hear any additional feedback, I think I'll open this for
voting at the end of the week.

I've looked once more into my “naming remark” and realized that the
display_ prefix might actually be misleading (instead of “just”
inconsistent) when compared to display_errors or
display_startup_errors, because display_error_function_args does not
control whether the arguments are displayed. It also controls whether
or not the arguments are visible to a registered error_handler, which is
quite different from just suppressing them from public display as done
by display_errors.

My suggestion of error_ignore_args thus still stands and I would
likely vote against the RFC with the current naming (despite being in
favor of the feature itself).

Best regards
Tim Düsterhus

Hi internals,

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.

https://wiki.php.net/rfc/display_error_function_args

Regards,
Calvin

If I don't hear any additional feedback, I think I'll open this for
voting at the end of the week.

I've changed the name again to try to address everyone's concerns;
because of this, I'll delay the voting by a week, especially since
it's a holiday on when I had originally intended to do so anyways.
Feedback would be appreciated.

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.

https://wiki.php.net/rfc/display_error_function_args

| Add a error_ignore_args, which potentially defaults to “0”. This is
| made an INI option, as some users may want to disable the feature by
| enabling this option, at least for production (e.g. risks of untagged
| PII in logs, size of logs, format compatibility with older versions of
| PHP).

I'm generally not in favour of new ini settings. I also don't think this
is going to help a lot, as many people will likely not change the
default.

But, I am especially not keen on "negative names". Names that include
"ignore" or "disable" for example. If you must have an ini setting, it
ought to be something like "include_error_args" (defaulting to "0", I
suspect).

The confusion in
https://github.com/php/php-src/pull/12276#pullrequestreview-4035216287
also explains why I feel this.

cheers,
Derick

--
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Tim, would this name be OK? I also have a preference towards a non-inverted name (it was more overhead to keep track of it), but I do see wanting it consistent.

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.

https://wiki.php.net/rfc/display_error_function_args

Have you done any benchmarking on this? What is the performance impact when it is enabled versus disabled? That information will be useful if this passes so that users can understand not just the security impact of having this information reported in logs, but the performance impact.

--
Matthew Weier O'Phinney
mweierophinney@gmail.com
https://mwop.net/
he/him

I haven't yet. I suppose the usual benchmark suite PHP runs might not be interesting for this seeing as they probably shouldn't be writing to the error log...

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.

https://wiki.php.net/rfc/display_error_function_args

Have you done any benchmarking on this? What is the performance impact when it is enabled versus disabled? That information will be useful if this passes so that users can understand not just the security impact of having this information reported in logs, but the performance impact.

--
Matthew Weier O'Phinney
mweierophinney@gmail.com
https://mwop.net/
he/him

FWIW, I actually did try running benchmark/benchmark.php. The difference is pretty much margin of error (somehow fewer instructions in some cases?), but I also don't expect to see much of any docrefs triggered in it either. For the sake of completeness:

Without:
{
"Zend/bench.php": {
"instructions": "1979721332"
},
"Zend/bench.php JIT": {
"instructions": "589555739"
},
"Symfony Demo 2.2.3": {
"instructions": "87285017"
},
"Symfony Demo 2.2.3 JIT": {
"instructions": "90024058"
},
"Wordpress 6.2": {
"instructions": "244605957"
},
"Wordpress 6.2 JIT": {
"instructions": "211892436"
}
}
With:
{
"Zend/bench.php": {
"instructions": "1979721328"
},
"Zend/bench.php JIT": {
"instructions": "589555784"
},
"Symfony Demo 2.2.3": {
"instructions": "87285011"
},
"Symfony Demo 2.2.3 JIT": {
"instructions": "90023734"
},
"Wordpress 6.2": {
"instructions": "244606014"
},
"Wordpress 6.2 JIT": {
"instructions": "211892519"
}
}

You can try it yourself with this patch (set error_include_args as needed):

diff --git a/benchmark/benchmark.php b/benchmark/benchmark.php
index 0c2ac4c6010..6377c3ceb37 100644
--- a/benchmark/benchmark.php
+++ b/benchmark/benchmark.php
@@ -79,7 +79,8 @@ function runWordpress(bool $jit): array {
/* FIXME: It might be better to use a stable version of PHP for this command because we can't
* easily alter the phar file */
runPhpCommand([

•    '-d error_reporting=0',
  

•    '-d error_reporting=22527',
  

•    '-d error_include_args=1',
     'wp-cli.phar',
     'core',
     'install',
  

@@ -122,6 +123,8 @@ function runValgrindPhpCgiCommand(
'--',
$phpCgi,
'-T' . ($warmup ? $warmup . ',' : '') . $repeat,

•    '-d error_reporting=22527',
  

•    '-d error_include_args=1',
     '-d max_execution_time=0',
     '-d opcache.enable=1',
     '-d opcache.jit=' . ($jit ? 'tracing' : 'disable'),
  

I'm working on something that triggers a lot of docrefs in a hot loop, but I also don't know how interesting that would be seeing as if you're getting thousands of docref-triggered messages a second, your program probably has an issue.

Based on the feedback I had from my proposal for function arguments in
errors last week, I'd like to introduce an RFC for it. Please let me
know what you think and please raise any possible issues.

https://wiki.php.net/rfc/display_error_function_args

Have you done any benchmarking on this? What is the performance impact when it is enabled versus disabled? That information will be useful if this passes so that users can understand not just the security impact of having this information reported in logs, but the performance impact.

--
Matthew Weier O'Phinney
mweierophinney@gmail.com
https://mwop.net/
he/him

I've been doing a very stupid benchmark (let's call it Lhogstones):

<?php

/* -d error_include_args=X -d display_errors=0 -d error_log=/tmp/test */

$iter = isset($argv[1]) ? intval($argv[1]) : 10000;
$start = hrtime(true);
for ($i = 0; $i < $iter; $i++) {
hex2bin("ABC"); /* or like unlink("/") for something that does more */
}
$end = hrtime(true);
$total_ns = $end - $start;
$total = $total_ns / 1_000_000_000;

echo "Finished $iter iterations in $total sec\n";

?>

On an M1 Pro:

Iterations With Without
10000 0.025276917 0.016741333
100000 0.189566666 0.123559584
1000000 1.798127917 1.146331917
10000000 18.1332335 11.267384125

There is an impact from turning it on, but my feeling is that it would be pretty minor. If your code has a lot of warnings/errors, then my feeling is that errors should be fixed before you can or should measure performance. Calling php_error_docref in a tight loop isn't really normal behaviour. So, while there is an impact, I also don't think it matters too much. If people think the impact does matter and is significant, then I could add a vote to separate the production vs. development INI value.