<?php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved
  
  class BookSingleton {

    private $author = 'Gamma, Helm, Johnson, and Vlissides';
    private $title  = 'Design Patterns';
    private static $book = NULL;
    private static $isLoanedOut = FALSE;

    private function __construct() {
    }

    static function borrowBook() {
      if (FALSE == self::$isLoanedOut) {
        if (NULL == self::$book) {
           self::$book = new BookSingleton();
        }
        self::$isLoanedOut = TRUE;
        return self::$book;
      } else {
        return NULL;
      }
    }

    function returnBook(BookSingleton $bookReturned) {
        self::$isLoanedOut = FALSE;
    }

    function getAuthor() {return $this->author;}

    function getTitle() {return $this->title;}

    function getAuthorAndTitle() {
      return $this->getTitle() . ' by ' . $this->getAuthor();
    }

  }

?>