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Date: Thu, 5 Mar 2026 02:15:00 +0530
Message-ID: <CANLbj-qEPv6Wp4kSBgMs4GSGek_sr-4noZzPGaKsRmZgskDCJA@mail.gmail.com>
Subject: Re: [PHP-DEV] Displaying function arguments in errors
To: Calvin Buckley <calvin@cmpct.info>
Cc: PHP internals <internals@lists.php.net>
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From: ayesh@php.watch (Ayesh Karunaratne)

> I'm dusting off an old PR (GH-12276) I had that I had lying around that
> I think would be quite useful.
>
> Currently, errors in PHP can optionally return some parameter info in
> the docref call; in practice, few do so, except a few functions.
> This means if you're looking at a PHP error log, you can see what
> function is failing, but often not why without having to step debug it.
>
> What this PR will do is effectively turn this:
>
> ```
> Warning: unlink('/tmp'): Operation not permitted in /Users/calvin/src/chmod.php on line 3
>
> Warning: chown('/', 'calvin'): Operation not permitted in /Users/calvin/src/chmod.php on line 4
>
> Warning: chmod('/', 511): Operation not permitted in /Users/calvin/src/chmod.php on line 5
> ```
>
> Into this:
>
> ```
> Warning: unlink(/tmp): Operation not permitted in /Users/calvin/src/chmod.php on line 3
>
> Warning: chown(): Operation not permitted in /Users/calvin/src/chmod.php on line 4
>
> Warning: chmod(): Operation not permitted in /Users/calvin/src/chmod.php on line 5
> ```
>
> This should make it easier at a glance to see what goes wrong in a log.
> Because this reuses the current infrastructure for stack traces, this
> will also handle i.e. sensitive parameters for free.
>
> Because this may not always be desirable (i.e. log size, logging PII
> that wasn't tagged as sensitive, not having to rewrite every .phpt
> file), this will be an INI option. We can vote on what should be the
> defaults, and what should be done with tests. Note that the docref's
> parameter will be displayed if it's turned off (or i.e. out of memory).
>
> I think this will almost certainly need an RFC; if there's interest,
> I'll start working on that.
>
> Regards,
> Calvin
>
> PR is at: https://github.com/php/php-src/pull/12276

Hi Calvin,
I'm glad you are reviving that PR. I think this will be a nice improvement.

I was worried that large parameters might pollute the error logs. I
tested the PR, and it was a pleasant surprise that the parameters
shown in the warning message also follow
`zend.exception_string_param_max_len` INI setting and get trimmed to
that length.

In the RFC, you might also want to mention in the PR that the
parameters will be trimmed (just like SensitiveParameters are masked),
and code like this will not write the whole parameter to the error
log:

```php
ini_set('display_error_function_args', '1');
file_put_contents('/', random_bytes(512))
```

Best regards,
Ayesh.