Description:
------------
Its seems, PHP should show error with type E_WARNING. If it's wrong, then i think, NUL-byte is unexpected there.

Reproduce code:
---------------
<?php
// ASCII in hex
function show_callback($m) {return '['.dechex(ord($m[0])).']';}
function show($result) {echo preg_replace_callback('~\W~','show_callback',$result)."\n";}
// Execution
for ($i = 0; $i < 5; $i++)
{
 $callback = create_function('$php','undefined();');
 $string = substr($callback,0); // or other function, for example, strval() or str_replace()...
 show($string);
}
?>

Expected result:
----------------
It seems, PHP should show error with type E_WARNING. If it's wrong, then I think, NUL-byte is unexpected there. Sorry for my English, I know, it's difficult to read.
Thanks!

Actual result:
--------------
[0]lambda_35
[0]lambda_36
[0]lambda_37
[0]lambda_38
[0]lambda_39