visitor

 <?php
abstract class Visitee
{
    abstract function accept(Visitor $visitorIn);
}
class BookVisitee extends Visitee
{
    private $author;
    private $title;
    function __construct($title_in, $author_in)
    {
        $this->author = $author_in;
        $this->title  = $title_in;
    }
    function getAuthor()
    {
        return $this->author;
    }
    function getTitle()
    {
        return $this->title;
    }
    function accept(Visitor $visitorIn)
    {
        $visitorIn->visitBook($this);
    }
}
class SoftwareVisitee extends Visitee
{
    private $title;
    private $softwareCompany;
    private $softwareCompanyURL;
    function __construct($title_in, $softwareCompany_in, $softwareCompanyURL_in)
    {
        $this->title              = $title_in;
        $this->softwareCompany    = $softwareCompany_in;
        $this->softwareCompanyURL = $softwareCompanyURL_in;
    }
    function getSoftwareCompany()
    {
        return $this->softwareCompany;
    }
    function getSoftwareCompanyURL()
    {
        return $this->softwareCompanyURL;
    }
    function getTitle()
    {
        return $this->title;
    }
    function accept(Visitor $visitorIn)
    {
        $visitorIn->visitSoftware($this);
    }
}
abstract class Visitor
{
    abstract function visitBook(BookVisitee $bookVisitee_In);
    abstract function visitSoftware(SoftwareVisitee $softwareVisitee_In);
}
class PlainDescriptionVisitor extends Visitor
{
    private $description = NULL;
    function getDescription()
    {
        return $this->description;
    }
    function setDescription($descriptionIn)
    {
        $this->description = $descriptionIn;
    }
    function visitBook(BookVisitee $bookVisiteeIn)
    {
        $this->setDescription($bookVisiteeIn->getTitle() . '. written by
' . $bookVisiteeIn->getAuthor());
    }
    function visitSoftware(SoftwareVisitee $softwareVisiteeIn)
    {
        $this->setDescription($softwareVisiteeIn->getTitle() . '. made by ' . $softwareVisiteeIn->getSoftwareCompany() . '. website at ' . $softwareVisiteeIn->getSoftwareCompanyURL());
    }
}
class FancyDescriptionVisitor extends Visitor
{
    private $description = NULL;
    function getDescription()
    {
        return $this->description;
    }
    function setDescription($descriptionIn)
    {
        $this->description = $descriptionIn;
    }
    function visitBook(BookVisitee $bookVisiteeIn)
    {
        $this->setDescription($bookVisiteeIn->getTitle() . '...!*@*! written !*! by !@! ' . $bookVisiteeIn->getAuthor());
    }
    function visitSoftware(SoftwareVisitee $softwareVisiteeIn)
    {
        $this->setDescription($softwareVisiteeIn->getTitle() . '...!!! made !*! by !@@! ' . $softwareVisiteeIn->getSoftwareCompany() . '...www website !**! at http://' . $softwareVisiteeIn->getSoftwareCompanyURL());
    }
}
writeln('BEGIN TESTING VISITOR PATTERN');
writeln('');
$book         = new BookVisitee('Design Patterns', 'Gamma, Helm, Johnson, and
Vlissides');
$software     = new SoftwareVisitee('Zend Studio', 'Zend Technologies', 'www.zend.com');
$plainVisitor = new PlainDescriptionVisitor();
acceptVisitor($book, $plainVisitor);
writeln('plain description of book: ' . $plainVisitor->getDescription());
acceptVisitor($software, $plainVisitor);
writeln('plain description of software: ' . $plainVisitor->getDescription());
writeln('');
$fancyVisitor = new FancyDescriptionVisitor();
acceptVisitor($book, $fancyVisitor);
writeln('fancy description of book: ' . $fancyVisitor->getDescription());
acceptVisitor($software, $fancyVisitor);
writeln('fancy description of software: ' . $fancyVisitor->getDescription());
writeln('END TESTING VISITOR PATTERN');
//double dispatch any visitor and visitee objects
function acceptVisitor(Visitee $visitee_in, Visitor $visitor_in)
{
    $visitee_in->accept($visitor_in);
}
function writeln($line_in)
{
    echo $line_in . "<br/>";
}
?>