ID: 36983
Updated by: [EMAIL PROTECTED]
Reported By: crisp at tweakers dot net
-Status: Assigned
+Status: Closed
Bug Type: PCRE related
Operating System: *
PHP Version: 5.1.2, 4.4.2
Assigned To: andrei
New Comment:
PHP 5.2 already has a preg_last_error() function. It was choosen to not
emit a warning, but rather making them acessible though that function.
If you append the line below to your scipt, it will print true:
var_dump(preg_last_error() === PREG_BACKTRACK_LIMIT_ERROR);
Previous Comments:
------------------------------------------------------------------------
[2006-04-05 23:01:05] crisp at tweakers dot net
Just a small update on this. PCRE is actually issuing an error;
specifically PCRE_ERROR_MATCHLIMIT (-8)
Apparently when PCRE goes into backtracking it will try any combination
of the OR'ed subpattern resulting into over 10.000.000 calls to match().
Obviously there is no construction that first checks if (and where) a
possible alternative defined as an OR can match within the part that is
being backtracked.
So this seems to be defined behaviour of PCRE (but it could use
improvement if even a simple case like the one I constructed already
triggers this behaviour), but my question now is why does PHP not raise
a warning or error when PCRE exits with one?
------------------------------------------------------------------------
[2006-04-05 17:25:11] crisp at tweakers dot net
Indeed this seems to be an issue with PCRE; version 6.6 still has this
problem so I'll try my luck with the PCRE team.
Notwithstanding I don't believe 'bogus' is the right status for this
bug since it is an actual issue, just not with PHP (although afaik PHP
still ships with PCRE version 6.4).
I'll just put this bug to 'closed'
------------------------------------------------------------------------
[2006-04-05 12:41:15] crisp at tweakers dot net
Description:
------------
It seems that when PCRE needs to backtrack more than 20 characters in
order to evaluate an OR'ed expression the results of a preg_match_all
are incorrect/incomplete.
See below code as an example.
Reproduce code:
---------------
$foo = 'foo# bar# abcdefghijklmnopqrst bla#';
echo '$foo = ', $foo, "\n";
preg_match_all('/([a-y]|z)+#/', $foo, $matches1);
preg_match_all('/([a-y]+|z)+#/', $foo, $matches2);
print_r($matches1[0]);
print_r($matches2[0]);
$foo = 'foo# bar# abcdefghijklmnopqrstu bla#';
echo '$foo = ', $foo, "\n";
preg_match_all('/([a-y]|z)+#/', $foo, $matches1);
preg_match_all('/([a-y]+|z)+#/', $foo, $matches2);
print_r($matches1[0]);
print_r($matches2[0]);
Expected result:
----------------
both expressions for both strings should give the following output:
Array
(
[0] => foo#
[1] => bar#
[2] => bla#
)
Actual result:
--------------
The last expression gives the following output on the last string:
Array
(
[0] => foo#
[1] => bar#
)
The last match on bla# is missing in the result for the preg_match_all
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=36983&edit=1
