PHP Design Patterns .

PHP Design Patterns State

About the State

In the State Pattern a class will change it's behavior when circumstances change.

In this example, the BookContext class holds an implementation of the BookTitleStateInterface, starting with BookTitleStateStars. BookTitleStateStars and BookTitleStateExclaim will then replace each other in BookContext depending on how many times they are called.

BookContext.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
  
  include_once('Book.php');
  include_once('BookTitleStateStars.php');


  class BookContext {
      
    private $book = NULL;
    private $bookTitleState = NULL; 
    
    //bookList is not instantiated at construct time
    public function __construct($book_in) {
      $this->book = $book_in;
      $this->setTitleState(new BookTitleStateStars());
    }


    public function getBookTitle() {
      return $this->bookTitleState->showTitle($this);
    }  


    public function getBook() {
      return $this->book;
    }


    public function setTitleState($titleState_in) {
      $this->bookTitleState = $titleState_in;
    }


  }

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BookTitleStateInterface.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved


  interface BookTitleStateInterface {
      
    public function showTitle($context_in);


  }

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BookTitleStateExclaim.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
  
  include_once('Book.php');
  include_once('BookTitleStateInterface.php');
  include_once('BookTitleStateStars.php');
  
  class BookTitleStateExclaim implements BookTitleStateInterface {
      
    private $titleCount = 0; 
    
    public function showTitle($context_in) {
      $title = $context_in->getBook()->getTitle();
      $this->titleCount++;
      $context_in->setTitleState(new BookTitleStateStars());
      return Str_replace(' ','!',$title);
    }
  }

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BookTitleStateStars.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved
  
  include_once('Book.php');
  include_once('BookTitleStateInterface.php');
  include_once('BookTitleStateExclaim.php');
  
  class BookTitleStateStars implements BookTitleStateInterface {
      
    private $titleCount = 0; 
    
    public function showTitle($context_in) {
      $title = $context_in->getBook()->getTitle();
      $this->titleCount++;
      if (1 < $this->titleCount) {
        $context_in->setTitleState(new BookTitleStateExclaim); 
      }
      return Str_replace(' ','*',$title);
    }
  }

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Book.php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved
  
  class Book {


    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 getAuthorAndTitle() {
      return $this->getTitle() . ' by ' . $this->getAuthor();
    }


  }

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testState.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved


  include_once('Book.php');
  include_once('bookContext.php');


  define('BR', '<'.'BR'.'>');


  echo 'BEGIN TESTING STATE PATTERN'.BR;
  echo BR;
  
  $book = new Book('PHP for Cats','Larry Truett');;
  
  $context = new bookContext($book);
  
  echo 'test 1 - show name'.BR;
  echo $context->getBookTitle();
  echo BR.BR;


  echo 'test 2 - show name'.BR;
  echo $context->getBookTitle();
  echo BR.BR;
  
  echo 'test 3 - show name'.BR;
  echo $context->getBookTitle();
  echo BR.BR;
  
  echo 'test 4 - show name'.BR;
  echo $context->getBookTitle();
  echo BR.BR;


  echo 'END TESTING STATE PATTERN'.BR;

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output of testState.php

BEGIN TESTING STATE PATTERN


test 1 - show name
PHP*for*Cats


test 2 - show name
PHP*for*Cats


test 3 - show name
PHP!for!Cats


test 4 - show name
PHP*for*Cats


END TESTING STATE PATTERN

References

Design Patterns
Design Patterns by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides

PHP 5
The Official PHP web site
Core PHP Programming, 3rd Edition by Leon Atkinson and Zeev Suraski

Comments Comments are left by visitors to FluffyCat.com and may or may not be accurate.

Comment by Larry on 2012-08-27 Rate this Comment

This is the first pattern example I've done for PHP which is based on the same pattern example I did for Java. This example and Java Design Patterns State are almost identical.

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