ID: 49550 User updated by: spoon dot reloaded at gmail dot com Reported By: spoon dot reloaded at gmail dot com Status: Bogus Bug Type: PCRE related Operating System: Linux PHP Version: 5.3.0 New Comment:
I found a solution: echo preg_match('/^|(.(?:|(?1)))$/', 'ab'), "\n"; but I still don't understand why the other one doesn't work Previous Comments: ------------------------------------------------------------------------ [2009-09-14 10:49:09] spoon dot reloaded at gmail dot com But that still wouldn't explain why stuff like balanced parentheses matching /^(\(((?>[^()]+)|(?1))*\))$/ works. I am still waiting for an explanation on my example. ------------------------------------------------------------------------ [2009-09-14 10:24:41] spoon dot reloaded at gmail dot com Nevermind, so I think the reason is that PCRE differs from Perl in that a recursive "sub-"pattern (i.e. ?1, ?2, etc. but not ?0) only matches exactly what was matched before by that subgroup, even if there are other unused possibilities by that group. Is that correct? ------------------------------------------------------------------------ [2009-09-14 10:06:30] spoon dot reloaded at gmail dot com > Remove the $ and it works. Yeah but that changes the meaning. I want to enforce that it matches the entire string, and it doesn't do that. To give another example without a $, consider: echo preg_match('/^(|.(?1))x/', 'abx'), "\n"; Again, it works in Perl, but not in PHP. ------------------------------------------------------------------------ [2009-09-14 09:51:16] j...@php.net Remove the $ and it works. And remember that PCRE != Perl. ------------------------------------------------------------------------ [2009-09-14 08:16:30] spoon dot reloaded at gmail dot com Description: ------------ I have a recursive PCRE pattern that should match any string (it does in Perl), but it fails to match a very simple string in PHP. I have reproduced this on both 5.2 and 5.3. Reproduce code: --------------- echo preg_match('/^(|.(?1))$/', 'ab'), "\n"; Expected result: ---------------- I expect it to print "1", because the pattern matches. In Perl, 'ab' =~ /^(|.(?1))$/ indeed matches. In fact, this pattern should match any string, because it matches either an empty string, or any character followed by something that matches the main part of the pattern itself (which matches any string). Actual result: -------------- It prints "0", indicating that it did not match. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=49550&edit=1