php - why session data not being destroy? -

i have simple php simple scripts. 1 display login user, , other 1 log out. these code fragments larger file. anyway, first executed login script , enter user name, user name showed fine. next executed logout. if entered login page again, expected login_user empty, not. older login_user name still there. if clear cache , bring login page again, login_user gone. how clear session data good? here login.php

<?php    session_start();   $_session['myerror']="xxx";    displayloginuser();    function displayloginuser()   {      if (isset ($_session['login_user']))      {         echo $_session['login_user'];      }   } // end displayloginuser ?> 

here logout.php

<?php  // note none of statements below seem clear login_user     $_session['login_user'] = " ";  unset ($_session['login_user']);  session_destroy();  header("location: library.php"); ?> 

try this:

session_start(); $_session = array(); session_destroy(); 

will destroy session , variables no need unset() or else