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Date: Fri, 03 Oct 2025 17:02:10 +0200
To: Ayesh Karunaratne <ayesh@php.watch>
Cc: Alexandre Daubois <alex.daubois+php@gmail.com>, Juliette Reinders Folmer
 <php-internals_nospam@adviesenzo.nl>, internals@lists.php.net
Subject: Re: [PHP-DEV] [DISCUSSION] Validating regex pattern
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

Am 2025-10-02 13:03, schrieb Ayesh Karunaratne:
> I completely agree with this and the previous reply from Juliette.

I also fully agree with Juliette: This is something that needs to be 
done in ext/pcre.

> A `PREG_THROW_ON_ERROR` flag would be the best of both worlds:
> 
>  - Provides a nice safe-guard against potentially invalid regexps and
> surfaces them up as an exception.
>  - Provides validation functionality with engine-provided error 
> messages.
>  - We do not need to keep up with the regex engines because validation
> is done by the engine.
>  - Works similar to the `JSON_THROW_ON_ERROR` flag.

I however don't think that PREG_THROW_ON_ERROR is the best solution 
here. A flag that effectively *always* needs to be passed is not good 
API design and functions like `preg_replace()` don't currently support 
flags. While it would definitely increase the scope of an RFC, I second 
Thomas' notion of providing a new (object-oriented) pcre API that would 
also allow for passing modifiers independently of the expression itself, 
avoiding the need for delimiters (and escaping them when dynamically 
constructing a regex).

Best regards
Tim Düsterhus