On 1-10-2025 11:01, Alexandre Daubois wrote:
Two propositions emerged from the issue: either create a dedicated
"preg_validate()" function, or add a new flag to "filter_var()",
namely FILTER_VALIDATE_REGEX_PATTERN.
I would be in favor of the latter. The approach and implementation
would surely be simpler. I don't feel like we should do advanced error
management. Knowing if a pattern is valid or not would suffice for the
vast majority of cases.
I don't think the second approach would require an RFC.
I'd love to see more robust ways to validate regexes, but I do not like
this proposal, as any solution involving the filter extension feels wrong.
Some background:
Historically, PHP supported three regex engines (POSIX, PCRE,
Oniguruma). The POSIX engine was dropped in PHP 7.0 and there is a draft
RFC to drop support for Oniguruma [1], however, that still means that at
this time PHP supports two different regex engines, which each have
their own criteria for when a regex is a valid pattern, and for
Oniguruma supports a multitude of regex dialects [2].
Involving an unrelated extension (filter), which may be unavailable (can
be disabled [3]), in the validation just complicates things.
It also makes the `FILTER_VALIDATE_REGEX_PATTERN` flag highly ambiguous
as it is unclear against which engine/dialect the regex would be validated.
It is my opinion that any regex pattern validation should be done in the
same extension realm as the extension which will use the regex.
Maybe the error code flags returned via `preg_last_error()` [4] should
be made more specific to allow for detecting when a regex function
failed due to an error in the regex.
Maybe the extensions should get a "throw on invalid regex" option,
either via an ini flag, a new function parameter or via an existing
function like `mb_regex_set_options()`.
Maybe there should be a `preg_validate()` function (and a
`mb_ereg_validate()` function for that matter).
I'm not sure what the best solution is, but going with an illogical
solution just to try and avoid the RFC process is not the way to go IMO.
Smile,
Juliette
1: https://wiki.php.net/rfc/eol-oniguruma
2: https://www.php.net/manual/en/function.mb-regex-set-options.php
2: https://www.php.net/manual/en/filter.installation.php
3: https://www.php.net/manual/en/function.preg-last-error.php
