Description:
------------
when replacing an utf-8 string containing the character '?' (hex: c3a0) With the function preg_replace, and the pattern '\s', it changes the second byte of this character.

Using the pattern '\t\f\r\n' which is supposed to be the same as \s it works perfectly.


I have tried with other utf-8 characters and it seems to work.

Reproduce code:
---------------
<?
$text = utf8_encode("this is a test ?t");
echo bin2hex($text)."\r\n";
$text1 = preg_replace("'([\t\f\r\n])+'", " ", $text);
echo bin2hex($text1)."\r\n";
echo $text1."\r\n";;
$text2 = preg_replace("'([\s])+'", " ", $text);
echo bin2hex($text2)."\r\n";
echo $text2;
?>

Expected result:
----------------
746869732069732061207465737420c3a074
746869732069732061207465737420c3a074
this is a test &#9500;?t
746869732069732061207465737420c3a074
this is a test &#9500;?t

Actual result:
--------------
746869732069732061207465737420c3a074
746869732069732061207465737420c3a074
this is a test &#9500;?t
746869732069732061207465737420c32074
this is a test &#9500; t