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Bug #16040 nested preg_replace_callback()'s won't work
Submitted: 2002-03-13 07:31 UTC Modified: 2002-06-16 01:00 UTC
Votes:3
Avg. Score:5.0 ± 0.0
Reproduced:3 of 3 (100.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: markus dot pfefferle at web dot de Assigned:
Status: No Feedback Package: PCRE related
PHP Version: 4.1.1 OS: Linux
Private report: No CVE-ID: None
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 [2002-03-13 07:31 UTC] markus dot pfefferle at web dot de
A preg_replace_callback() that calls a callback function which in turn makes use of a preg_replace_callback() function too, will not work correctly. The first preg_replace_callback() will substitute gibberisch even though the callback function returned a valid string.

Example:

function funcB($arr)
{
  ...
  return $whatever;
}

function funcA($arr)
{
  ...
  $t = preg_replace_callback("/%value([0-9]+)%/", "funcB", $someotherhaystack)
  return $t; // $t still makes sense here
}

echo preg_replace_callback("/%text([0-9]+)%/", "funcA", $haystack);

// but whatever funcA returned, just some gibberisch is substituted for /%text[0-9]+%/

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 [2002-04-09 17:00 UTC] jimw@php.net
the code below works fine for me. please provide a complete example of code that fails.

function funcB($arr) {
  return 'whatever';
}
function funcA($arr) {
  $someotherhaystack = '%value1% foo %value2%';
  $t = preg_replace_callback("/%value([0-9]+)%/", "funcB", $someotherhaystack);
  return $t; // $t still makes sense here
}

$haystack = '%text12% bar %text13%';
echo preg_replace_callback("/%text([0-9]+)%/", "funcA", $haystack);
 [2002-06-16 01:00 UTC] php-bugs at lists dot php dot net
No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
 [2008-12-18 19:44 UTC] ilatypov at infradead dot org
This also holds true for yesterday's CVS snapshot of PHP6, in Windows XP.

I tried installing MediaWiki with the PHP6 snapshot and found that the table prefix replacement in includes/db/Database.php:replaceVars() returns corrupt data sporadically.

I found that pref_replace_callback() was the source of the corruption.

This statement:

        $ins = preg_replace_callback( '/\/\*(?:\$wgDBprefix|_)\*\/([a-zA-Z_0-9]*)/',
            array( &$this, 'tableNameCallback' ),
            $ins );

called the tableName() method through the callback tableNameCallback().  The former method returned a proper string but the end result in $ins was corrupted.

On finding this earlier report, I looked closer at the Database.tableName() method and found a call to preg_match() there.
 [2008-12-18 19:46 UTC] ilatypov at infradead dot org
I downgraded to PHP 5.2.8, and the nested regexp replacement worked.
 
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