web - PHP Login Form Session Variable Destroying -

i new php , creating login screen session variable. trying destroy or unset session variable when logging out doesn't seem work.

my session variable:

$_session['currentuser']

this button should end session:

<input type="submit" name="logout" id="logout" value="log out">

when pressing button:

if(isset($_post['logout'])) {     session_unset();       session_destroy();  }

my practice, set session variable random:

$_session['currentuser'] = time(); session_destroy();

and reload/refresh page. example:

header('location: /'); die;

if not redirect after session destruction, page render as if session not destroyed (html render...)

Breniser