<form ........>.......<input type="checkbox" name="list[]" value="name1" />
.........<input type="checkbox" name="list[]" value="name2" />
</form>

$mark_list = ( !empty($_POST['list']) ) ? $_POST['list'] : 0;

for($i = 0; $i < count($mark_list); $i++) {
................
}

$my_var = 'some content';
include('user.php');

echo $my_var;

define('ROOT_PATH', $_SERVER['DOCUMENT_ROOT'] . '/');

define(ROOT_PATH . 'LIB_PATH', 'my_lib/');
define(ROOT_PATH . 'INC_PATH', 'my_includes/');

<?php
. . .
if ( have_rights($user) ) {
    header ("Cache-Control: must-revalidate, post-check=0, pre-check=0");
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Length: ' . filesize(тынц тынц));
    header('Content-Disposition: attachment; filename=' . basename(тынц тынц));
    header("Content-Transfer-Encoding: binary");

   readfile(тынц тынц);
} else {
   echo 'несанкционированный доступ запрещён';
}
?>