ID: 38899
User updated by: mike at we11er dot co dot uk
Reported By: mike at we11er dot co dot uk
Status: Open
Bug Type: *Regular Expressions
Operating System: Windows
PHP Version: 5.1.6
New Comment:
OK, sorry for so many posts... but I'm still having problems. The
actual regex i'm using is much more complicated, so I'm simpifying
here:
preg_match("/(((test))?)a\\3/", "a") returns FALSE
preg_match("/(((test))?)a\\3/", "testatest") returns TRUE
The part I need to reference is nested within an outer part that is
optional. Even adding extra parentheses doesn't solve the problem.
Previous Comments:
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[2006-09-20 14:14:34] mike at we11er dot co dot uk
Ah! I got a solution, though I'm still not sure what the correct
behaviour of the original regex should be.
preg_match("/((test)?)a\\1/", "a");
Wrapping another set of parentheses around the optional part works.
------------------------------------------------------------------------
[2006-09-20 13:40:30] mike at we11er dot co dot uk
I just realised the example code might be slightly ambiguous since the
(.)? could match the 'a' itself.
echo preg_match("/(test)?a\\1/", "a");
is a better example and returns false.
------------------------------------------------------------------------
[2006-09-20 13:34:32] mike at we11er dot co dot uk
I should also add that this happens with preg_split.
------------------------------------------------------------------------
[2006-09-20 13:24:12] mike at we11er dot co dot uk
Description:
------------
echo preg_match("/(.)?a\\1/", "a");
returns "0"
But since the back reference is to an optional item, if that item does
not exist, then the back reference should just be blank and thus the
above should match "a", i.e. nothing + 'a' + nothing
This is actually stopping quite an important feature from being
developed so I'd appreciate a speedy response. It might be something
I'm doing wrong, or maybe this isn't supported (but i think it should
be).
Thanks in advance.
Reproduce code:
---------------
echo preg_match("/(.)?a\\1/", "a");
Expected result:
----------------
Should return TRUE.
Actual result:
--------------
returns FALSE.
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Edit this bug report at http://bugs.php.net/?id=38899&edit=1
