[php-src] Issue #9289: Function to validate regular expression

Issue: https://github.com/php/php-src/issues/9289 Author: timint ### Description I have been missing a core function in PHP to validate a regular expression. I am therefore proposing something like preg_validate(). There are some workarounds mentioned in this StackOverflow thread. But from my understanding they will all produce a PHP warning that needs to be suppressed. https://stackoverflow.com/questions/4440626/how-can-i-validate-regex What are your thoughts and opinions on implementing a regex syntax validator?