Req #77521 [Com]: Validate regexes

Edit report at https://bugs.php.net/bug.php?id=77521&edit=1 ID: 77521 Comment by: danack@php.net Reported by: flip101 at gmail dot com Summary: Validate regexes Status: Open Type: Feature/Change Request Package: PCRE related Operating System: Ubuntu 18.04 PHP Version: 7.3.1 Block user comment: N Private report: N New Comment: I believe using preg_last_error() and silencing the preg_match error gives a sane way to validate if a regex is acceptable to PCRE. $invalid_pattern = '/(\d+/'; $dummy_subject = ''; @preg_match($invalid_pattern, $dummy_subject); $lastError = preg_last_error(); if ($lastError) { echo "something was wrong with the regex"; } Does that not cover detecting valid regexes? Admittedly getting the exact position of the error would be more than a little useful... Previous Comments: ------------------------------------------------------------------------ [2019-01-25 15:53:30] flip101 at gmail dot com Description: ------------ At the moment there is poor support to validate a regex. Since the inception of PHP where it was mainly used for creating personal home pages it's been used in more domains. Therefor having the ability to validate regexes would be a useful thing. As far as i know regexes can be validated to the PCRE engine in the following way: 1. make a custom error handler for PHP warning 2. register customer error handler 3. call preg_match with invalid regex 4. unregister custom error handler. 5. throw exception (or another way of dealing with the error) The motivation that led me here is the following library and issue: https://hoa-project.net/En/Literature/Hack/Compiler.html#PP_language https://github.com/hoaproject/Compiler/issues/15 But i believe there will be other projects now and in the feature that would benefit from a change in PHP PCRE module. I propose the following changes that should be backwards compatible: 1. Add constant PREG_INVALID_PATTERN (representing int 7) to https://secure.php.net/manual/en/function.preg-last-error.php which gets set when a pattern is an invalid regex. 2. Add a bool preg_validate_pattern($string) function that only calls the PCRE2 compile function and checks for succesful compilation. Skipping the step of actually trying to match a subject which is usually done. Test script: --------------- <?php $invalid_pattern = '/(\d+/'; $dummy_subject = ''; preg_match($invalid_pattern, $dummy_subject); ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=77521&edit=1