Description:
------------
post variables appear in session after 3 posts... 
$_GET
Array
(
)
$_POST
Array
(
    [search_didi] => asd
    [submitare] => Cautare simpla // !!!!!!!!!
    [submit] => Cautare           // !!!!!!!!!
)
$_SESSION
Array
(
    [submitare] => Cautare simpla // !!!!!!!!!
    [submit] => Cautare           // !!!!!!!!!
    [search_didi] => asd
)



Reproduce code:
---------------
Source code tested on php5.0.4, php5.1.2 (works fine on php4.4.0)
<?
session_start();

if(isset($_POST['submitare']) && ($_POST['submitare']=='Cautare simpla' || $_POST['submitare']=='Cautare avansata')){

        foreach($_SESSION as $key=>$value){
             if(preg_match("@_didi$@i",$key)){
                        unset($_SESSION["{$key}"]);
              }
        }
        foreach($_POST as $key=>$value){
                //echo $key."  ".$value."<hr>";
                if(preg_match("@_didi$@i",$key)){
                        echo $key."=".$value."<hr>";
                        $_SESSION["{$key}"]=$value;
                }
        }

}
echo "<pre>";
print_r($_GET);
print_r($_POST);
print_r($_SESSION);
echo "</pre>";
if(!isset($_POST['submitare']) && !isset($_GET['page'])){
        foreach($_SESSION as $key=>$value){
                if(preg_match("@_didi$@i",$key)){
                        unset($_SESSION["{$key}"]);
                }
        }
}
?>
<form action="" method="POST">
        Cauta: <input type="text" name="search_didi" value="" />
        <input type="hidden" name="submitare" value="Cautare simpla" />
        <input type="submit" name="submit" value="Cautare" />
</form>


Expected result:
----------------
$_GET
Array
(
)
$_POST
Array
(
    [search_didi] => asd
    [submitare] => Cautare simpla // !!!!!!!!!
    [submit] => Cautare           // !!!!!!!!!
)
$_SESSION
Array
(
    [search_didi] => asd
)