php session_destroy()和session_unset()区别

function session_clean1($logout=false)
{
$v=array();
foreach($_SESSION as $x=>$y)
if($x!="redirector"&&($x!="user"||$logout))
$v[]=$x;

foreach($v as $x)
unset($_SESSION[$x]);
return;
}

function session_clean2($logout=false)
{
foreach($_SESSION as $x=>$y)
if($x!="redirector"&&($x!="user"||$logout))
unset($_SESSION[$x]);
return;
}

function session_clean3($logout=false)
{
$s=($logout||!isset($_SESSION["user"]))?array():
array("user"=>$_SESSION["user"]);
if(isset($_SESSION["redirector"]))
$s["redirector"]=$_SESSION["redirector"];
$_SESSION=$s;
}

?>

// Initialize the session.
// If you are using session_name("something"), don't forget it now!
session_start();

// Unset all of the session variables.
$_SESSION = array();

// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
$params = session_get_cookie_params();
setcookie(session_name(), '', time() - 42000,
$params["path"], $params["domain"],
$params["secure"], $params["httponly"]
);
}

// Finally, destroy the session.
session_destroy();
?>