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Date: Wed, 1 Oct 2025 11:01:08 +0200
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Subject: [PHP-DEV] [DISCUSSION] Validating regex pattern
To: PHP internals list <internals@lists.php.net>
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From: alex.daubois+php@gmail.com (Alexandre Daubois)

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Hi everyone,

I stumbled across the following issue, proposing to add a way to validate
regex. [1]

There is currently no way of knowing if a regex pattern is valid, apart
from writing clunky code. [2]

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. Christoph thinks
that this should at least be announced on the mailing list, so here we are.

Looking forward to your feedback.

=E2=80=94 Alexandre Daubois

[1] https://github.com/php/php-src/issues/9289
[2] https://stackoverflow.com/questions/4440626/how-can-i-validate-regex

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<div dir=3D"ltr">Hi everyone,<div><br></div><div>I stumbled across the foll=
owing issue, proposing to add a way to validate regex. [1]</div><div><br></=
div><div>There is currently no way of knowing if a regex=C2=A0pattern is va=
lid, apart from writing clunky code. [2]</div><div><br></div><div>Two propo=
sitions emerged from the issue: either create a dedicated &quot;preg_valida=
te()&quot; function, or add a new flag to &quot;filter_var()&quot;, namely =
FILTER_VALIDATE_REGEX_PATTERN.</div><div><br></div><div>I would be in favor=
 of the latter. The approach and implementation would surely be simpler. I =
don&#39;t feel like we should do advanced error management. Knowing if a pa=
ttern is valid or not would suffice for the vast majority of cases.</div><d=
iv><br></div><div>I don&#39;t think the second approach would require=C2=A0=
an RFC. Christoph thinks that this should at least be announced on the mail=
ing list, so here we are.</div><div><br></div><div>Looking forward to your =
feedback.</div><div><br></div><div>=E2=80=94 Alexandre Daubois</div><div><b=
r></div><div>[1] <a href=3D"https://github.com/php/php-src/issues/9289">htt=
ps://github.com/php/php-src/issues/9289</a></div><div>[2]=C2=A0<a href=3D"h=
ttps://stackoverflow.com/questions/4440626/how-can-i-validate-regex">https:=
//stackoverflow.com/questions/4440626/how-can-i-validate-regex</a></div></d=
iv>

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