try {
    check_permission(PERM_ADDER);
    if (!isset($_POST['sid']) || !isset($_POST['book_id'])) {
        throw new UnexpectedValueException();
    }
    $sid = $_POST['sid'];
    $book_id = $_POST['book_id'];
    sql_begin();
    //creating book if necessary
    if ($book_id == -1) {
        //find the parent id
        $res = sql_pe("SELECT book_id, url FROM sources WHERE source_id = (SELECT parent_id FROM sources WHERE source_id=? LIMIT 1) LIMIT 1", array($sid));
        if (!isset($_POST['book_name']) || !$res[0]['book_id']) {
            throw new UnexpectedValueException();
        }
        $book_id = books_add($_POST['book_name'], $res[0]['book_id']);
        $res = sql_pe("SELECT url FROM sources WHERE source_id=? LIMIT 1", array($sid));
        books_add_tag($book_id, 'url:' . $res[0]['url']);
        download_url($res[0]['url']);
    }
    //bind
    sql_pe("UPDATE sources SET book_id=? WHERE source_id=? LIMIT 1", array($book_id, $sid));
    sql_commit();
    $res = sql_pe("SELECT book_name FROM books WHERE book_id=? LIMIT 1", array($book_id));
    $result['title'] = htmlspecialchars($res[0]['book_name']);
    $result['book_id'] = $book_id;
} catch (Exception $e) {
    $result['error'] = 1;
}
log_timing(true);
die(json_encode($result));

<?php

require 'lib/header.php';
require_once 'lib/lib_history.php';
if (isset($_POST['comment'])) {
    $comment = $_POST['comment'];
} else {
    $comment = '';
}
if (isset($_GET['set_id']) && ($set_id = $_GET['set_id'])) {
    $r = revert_changeset($set_id, $comment);
    header("Location:{$r}");
} elseif (isset($_GET['tf_rev']) && ($rev_id = $_GET['tf_rev'])) {
    revert_token($rev_id);
    header("Location:history.php");
} elseif (isset($_GET['dict_rev']) && ($rev_id = $_GET['dict_rev'])) {
    revert_dict($rev_id);
    header("Location:dict_history.php");
}
log_timing();