// example1.php
<?php
    require 'file.class.php';
    session_start();

    $f = new File('/etc/hosts');
    $f->seek(20);

    $_SESSION['f'] = $f;
? >

// example2.php
<?php
    require 'file.class.php';
    session_start();

    var_dump($_SESSION['f']);
? >