<?php

    session_start();

    $action = isset($_GET['action']) ? $_GET['action'] : NULL;

    if ($action == 'file-end') {
        session_write_close();
        $str = "This is a fairly large file\n";
        header('Content-Type: text/plain');
        header('Content-Length: '.(strlen($str) * 1000000));
        header('Content-Disposition: attachment; filename="largefile.txt"');
        for ($i = 0; $i < 1000000; $i++) {
            echo $str;
        }
    } else if ($action == 'file-noend') {
        $str = "This is a fairly large file\n";
        header('Content-Type: text/plain');
        header('Content-Length: '.(strlen($str) * 1000000));
        header('Content-Disposition: attachment; filename="largefile.txt"');
        for ($i = 0; $i < 1000000; $i++) {
            echo $str;
        }
    } else if ($action == 'click') {
        echo "
You clicked the link<br>
<a href='?action=null'>back</a>";
    } else {
        echo "
<a href='?action=file-end'>End the session and get the file</a><br>
<a href='?action=file-noend'>Get the file without ending the session</a><br>
<a href='?action=click'>Click the link</a>
";
    }