Re: Pre-RFC: adding a Regex\CompiledRegex class for compiling regular expressions

Hi Gina, > Hello internals, > > I spent the day prototyping an alternative to the PREG_THROW_ON_ERROR RFC as I'm not fully > a fan of the approach. > It can be found as the following PR: > https://github.com/php/php-src/pull/23868 > > The basic idea is to add a new Regex\CompiledRegex class that takes a pattern, and some boolean > modifiers, to compile a regular expression before passing it to the preg_* functions. I really like the idea, but I am not quite sure it fully replaces the PREG_THROW_ON_ERROR flag. Compilation errors are only half of the error story...the other half happens at match time, on patterns that compiled just fine. Consider this: ``` $r = preg_match('/(a+)+$/', str_repeat('a', 20) . '!'); var_dump($r); // bool(false) var_dump(preg_last_error_msg()); // string(25) "Backtrack limit exhausted" ``` As far as I understand, this class of errors (PREG_BACKTRACK_LIMIT_ERROR, PREG_RECURSION_LIMIT_ERROR, PREG_JIT_STACKLIMIT_ERROR, ...etc) depends on the subject, not the pattern, so no amount of validation at construction time can catch it. I think the proposal, though, removes a good part of the motivation for PREG_THROW_ON_ERROR, so now whether PHP should have a regex object that fails on compilation errors only and works with preg_* functions, or have a flag that guarantees the next line after a preg_* call only executes if the call left no error behind (or both?), is up to you and the people on this list to decide. I personally see the two as complementary rather than alternatives. That said, I really like and am in support of having a class that represents a compiled regex (for what my entirely non-voting opinion is worth), whether it replaces the flag or not. Best, Osama