Bug #81060 [Com]: The expression does not compile correctly

Edit report at https://bugs.php.net/bug.php?id=81060&edit=1 ID: 81060 Comment by: danack@php.net Reported by: vklimin at 510710 dot com Summary: The expression does not compile correctly Status: Not a bug Type: Bug Package: PCRE related Operating System: Debian 10 PHP Version: 8.0.6 Block user comment: N Private report: N New Comment: HI vklimin, While suprising, and possibly could be documented better, it appears that \Q and \E probably won't work for what you're trying to use them for: https://stackoverflow.com/a/20520551/778719 "Use preg_quote() instead of \Q \E if the delimiter may appear within \Q \E" Previous Comments: ------------------------------------------------------------------------ [2021-05-20 17:26:33] imsop@php.net My apologies, I see that \Q and \E change the meaning of the escape there. However, they *don't* change the handling of the delimiter, as that happens before the regex is even passed to PCRE. In other words, PCRE receives the regex \Q/\E and the modifiers \E/ hence the error message. ------------------------------------------------------------------------ [2021-05-20 17:17:55] vklimin at 510710 dot com The proposed solution is not correct var_dump( preg_match( '/\Q\/\E/', '/' ) ); Expected result: ---------------- int(1) Actual result: -------------- int(0) ------------------------------------------------------------------------ [2021-05-20 17:14:01] imsop@php.net Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php The first character of the regex determines the delimiter; any extra instances of that delimiter need to be escaped. var_dump( preg_match( '/\Q\/\E/', '/' ) ); ------------------------------------------------------------------------ [2021-05-20 17:09:51] vklimin at 510710 dot com Changed the name of the corresponding package ------------------------------------------------------------------------ [2021-05-20 17:07:16] vklimin at 510710 dot com Description: ------------ The expression does not compile correctly and generates a warning. Test script: --------------- var_dump( preg_match( '#\Q/\E#', '/' ) ); var_dump( preg_match( '/\Q/\E/', '/' ) ); Expected result: ---------------- int(1) int(1) Actual result: -------------- int(1) Warning: preg_match(): Unknown modifier '\' in [...][...] on line 1 bool(false) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=81060&edit=1