memento

 <?php
class BookReader
{
    private $title;
    private $page;
    function __construct($title_in, $page_in)
    {
        $this->setPage($page_in);
        $this->setTitle($title_in);
    }
    public function getPage()
    {
        return $this->page;
    }
    public function setPage($page_in)
    {
        $this->page = $page_in;
    }
    public function getTitle()
    {
        return $this->title;
    }
    public function setTitle($title_in)
    {
        $this->title = $title_in;
    }
}
class BookMark
{
    private $title;
    private $page;
    function __construct(BookReader $bookReader)
    {
        $this->setPage($bookReader);
        $this->setTitle($bookReader);
    }
    public function getPage(BookReader $bookReader)
    {
        $bookReader->setPage($this->page);
    }
    public function setPage(BookReader $bookReader)
    {
        $this->page = $bookReader->getPage();
    }
    public function getTitle(BookReader $bookReader)
    {
        $bookReader->setTitle($this->title);
    }
    public function setTitle(BookReader $bookReader)
    {
        $this->title = $bookReader->getTitle();
    }
}
// Client
writeln('BEGIN TESTING MEMENTO PATTERN');
writeln('');
$bookReader = new BookReader('Core PHP Programming, Third
Edition', '103');
$bookMark   = new BookMark($bookReader);
writeln('(at beginning) bookReader title: ' . $bookReader->getTitle());
writeln('(at beginning) bookReader page: ' . $bookReader->getPage());
$bookReader->setPage("104");
$bookMark->setPage($bookReader);
writeln('(one page later) bookReader page: ' . $bookReader->getPage());
$bookReader->setPage('2005'); //oops! a typo
writeln('(after typo) bookReader page: ' . $bookReader->getPage());
$bookMark->getPage($bookReader);
writeln('(back to one page later) bookReader page: ' . $bookReader->getPage());
writeln('');
writeln('END TESTING MEMENTO PATTERN');
function writeln($line_in)
{
    echo $line_in . "<br/>";
}
?>