Description:
------------
This is a bug in "stat" function, and I'm not quite sure which class this function belongs to.  Detailed message for the OS  and php version following:

OS message:
gao->:~$uname -a
Linux gaoqiang-VirtualBox 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:50 UTC 2011 i686 i686 i386 GNU/Linux

php version:
gao->:~$php -v
PHP 5.3.5-1ubuntu7.4 with Suhosin-Patch (cli) (built: Dec 13 2011 18:25:14) 
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies

Test script:
---------------
<?php 
$file="a.txt";
$fp=fopen($file,"a");
$st=stat($file);
echo "size= ";
echo $st["size"];
echo "\n";



fputs($fp,"test\n");
fclose($fp);


$st=stat($file);
echo "size= ";
echo $st["size"];
echo "\n";
?>

Expected result:
----------------
size=0
size=5

Actual result:
--------------
size=0
size=0