1 <?php 2  3 class Book 4 { 5     private $_author; 6     private $_title; 7  8     public function __construct($title, $author) 9     {10         $this->_author = $author;11         $this->_title = $title;12     }13 14     public function getAuthor()15     {16         return $this->_author;17     }18 19     public function getTitle()20     {21         return $this->_title;22     }23 24     public function getAuthorAndTitle()25     {26         return $this->getTitle().‘ by ‘.$this->getAuthor();27     }28 }29 30 31 class BookList implements \Countable, \Iterator32 {33     private $_books = [];34     private $_currentIndex = 0;35 36 37     public function addBook(Book $book)38     {39         $this->_books[] = $book;40     }41 42     public function removeBook(Book $bookToRemove)43     {44         foreach ($this->_books as $key => $book) {45             if ($book->getAuthorAndTitle() === $bookToRemove->getAuthorAndTitle()) {46                 unset($this->_books[$key]);47             }48         }49 50         $this->_books = array_values($this->_books);51     }52 53 54 55     /* 以下是接口部分 */56 57     public function count()58     {59         return count($this->_books);60     }61 62     public function current()63     {64         return $this->_books[$this->_currentIndex];65     }66 67     public function key()68     {69         return $this->_currentIndex;70     }71 72     public function next()73     {74         $this->_currentIndex++;75     }76 77     public function rewind()78     {79         $this->_currentIndex = 0;80     }81 82     public function valid()83     {84         return isset($this->_books[$this->_currentIndex]);85     }86 }87 88 89 90 91 $bookList = new BookList();92 $bookList->addBook(new Book(‘Learning PHP Design Patterns‘, ‘William Sanders‘));93 $bookList->addBook(new Book(‘Professional Php Design Patterns‘, ‘Aaron Saray‘));94 $bookList->addBook(new Book(‘Clean Code‘, ‘Robert C. Martin‘));95 96 foreach ($bookList as $book) {97     echo "<br/>";98     echo $book->getAuthorAndTitle();99 }

  1 <?php  2   3   4 class Book  5 {  6     private $_author;  7     private $_title;  8   9     public function __construct($title, $author) 10     { 11         $this->_author = $author; 12         $this->_title = $title; 13     } 14  15     public function getAuthor() 16     { 17         return $this->_author; 18     } 19  20     public function getTitle() 21     { 22         return $this->_title; 23     } 24  25     public function getAuthorAndTitle() 26     { 27         return $this->getTitle() . ‘ by ‘ . $this->getAuthor(); 28     } 29 } 30  31  32 class BookList implements \Countable 33 { 34     private $_books; 35  36     public function getBook($bookNumberToGet) 37     { 38         if (isset($this->_books[$bookNumberToGet])) { 39             return $this->_books[$bookNumberToGet]; 40         } 41  42         return null; 43     } 44  45     public function addBook(Book $book) 46     { 47         $this->_books[] = $book; 48     } 49  50     public function removeBook(Book $bookToRemove) 51     { 52         foreach ($this->_books as $key => $book) { 53             if ($book->getAuthorAndTitle() === $bookToRemove->getAuthorAndTitle()) { 54                 unset($this->_books[$key]); 55             } 56         } 57     } 58  59     public function count() 60     { 61         return count($this->_books); 62     } 63 } 64  65  66 class BookListIterator implements \Iterator 67 { 68     private $_bookList; 69     protected $_currentBook = 0; 70  71     public function __construct(BookList $bookList) 72     { 73         $this->_bookList = $bookList; 74     } 75  76     /** 77      * Return the current book 78      * @link http://php.net/manual/en/iterator.current.php 79      * @return Book Can return any type. 80      */ 81     public function current() 82     { 83         return $this->_bookList->getBook($this->_currentBook); 84     } 85  86     /** 87      * Move forward to next element 88      * @link http://php.net/manual/en/iterator.next.php 89      * @return void Any returned value is ignored. 90      */ 91     public function next() 92     { 93         $this->_currentBook++; 94     } 95  96     /** 97      * Return the key of the current element 98      * @link http://php.net/manual/en/iterator.key.php 99      * @return mixed scalar on success, or null on failure.100      */101     public function key()102     {103         return $this->_currentBook;104     }105 106     /**107      * Checks if current position is valid108      * @link http://php.net/manual/en/iterator.valid.php109      * @return boolean The return value will be casted to boolean and then evaluated.110      *       Returns true on success or false on failure.111      */112     public function valid()113     {114         return null !== $this->_bookList->getBook($this->_currentBook);115     }116 117     /**118      * Rewind the Iterator to the first element119      * @link http://php.net/manual/en/iterator.rewind.php120      * @return void Any returned value is ignored.121      */122     public function rewind()123     {124         $this->_currentBook = 0;125     }126 }127 128 129 130 131 132 133 134 $bookList = new BookList();135 $bookList->addBook(new Book(‘Learning PHP Design Patterns‘, ‘William Sanders‘));136 $bookList->addBook(new Book(‘Professional Php Design Patterns‘, ‘Aaron Saray‘));137 $bookList->addBook(new Book(‘Clean Code‘, ‘Robert C. Martin‘));138 139 $iterator = new BookListIterator($bookList);140 141 while ($iterator->valid()) {142     print "<br/>";143     print $iterator->current()->getAuthorAndTitle();144     $iterator->next();145 }