Description:
------------
OS: windows 2003 + IIS
PHP Version: 5.2.3

when I'm declare my own function myFun in a file func.php, I'm included into my main index.php, it's working at first time without any problem, when I'm using current page to submit data into the same page I'm getting the following error:

Fatal error: Cannot redeclare myfun() (previously declared in C:\accounts\panela\tmp\func.php:2) in C:\accounts\panela\tmp\func.php on line 2

I don't know whats the problem, I'm tried to solve this problem but I'm failed :(
this error is not logic, and the same script working in other php version like php 4.X


Reproduce code:
---------------
--- file: func.php ---
<?
function myFun($a,$b){ return $a+$b; }
?>

--- file: index.php ---
<?
include_once("func.php");
?>
<form name="FormName" action="" method="post">
	<input type="submit" value="Send">
</form>


Expected result:
----------------
this code when submit data into same php page.
I'm solved this problem by:


<?
if (!function_exists('myFun')) {                 
   function myFun($a,$b){ return $a+$b; }
}
?>

but unfortunately, when I'm refreshing the page I'm cant see my last editing in my function, for example, now I will edit the function to:

<?
if (!function_exists('myFun')) {                 
   function myFun($a,$b){ return $a*$b; }
}
?>
now with function_exists I cant see the new function $a*$b, but I'm see only the old function $a-$b.