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);

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".

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.

I downgraded to PHP 5.2.8, and the nested regexp replacement worked.