$book->addChapter("Chapter 7.1.3.2", "Chapter007132.html", $content_start . "<h2>Chapter 7.1.3.2</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
$book->addChapter("Chapter 7.1.3.3", "Chapter007133.html", $content_start . "<h2>Chapter 7.1.3.3</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
$book->addChapter("Chapter 7.1.3.4", "Chapter007134.html", $content_start . "<h2>Chapter 7.1.3.4</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
$log->logLine("Add Chapter 7.2.0.0");
// We went deep with Chapter 7.1.3.x, and sometimes the generating class knows exactly where it is anyway,
//  so instead of relying on multiple ->backLevel() calls, you can set the target level directly.
// This only works for going back in the hieracy. ->setCurrentLevel(1) (or less) equals ->rootLevel();
$book->setCurrentLevel(2);
$book->addChapter("Chapter 7.2", "Chapter00720.html", $content_start . "<h2>Chapter 7.2.0</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
$log->logLine("Add Chapter 7.3.0.0");
$book->addChapter("Chapter 7.3", "Chapter00730.html", $content_start . "<h2>Chapter 7.3.0</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
$log->logLine("Add Chapter 7.3.1.0");
$book->subLevel();
$book->addChapter("Chapter 7.3.1", "Chapter00731.html", $content_start . "<h2>Chapter 7.3.1</h2>\n" . $chapter7Body, false, EPub::EXTERNAL_REF_ADD, $fileDir);
// If you have nested chapters, you can call ->rootLevel() to return your hierachy to the root of the navMap.
$book->rootLevel();
$log->logLine("Add TOC");
$book->buildTOC();
$book->addChapter("Log", "Log.html", $content_start . $log->getLog() . "\n</pre>" . $bookEnd);
if ($book->isLogging) {
    // Only used in case we need to debug EPub.php.
    $epuplog = $book->getLog();
    $book->addChapter("ePubLog", "ePubLog.html", $content_start . $epuplog . "\n</pre>" . $bookEnd);
}
$book->finalize();
// Finalize the book, and build the archive.
// This is not really a part of the EPub class, but IF you have errors and want to know about them,
//  they would have been written to the output buffer, preventing the book from being sent.
//  This behaviour is desired as the book will then most likely be corrupt.
//  However you might want to dump the output to a log, this example section can do that:
/*