常见的PHP五种设计模式小结

<?php
interface IUser
{
 function getName();
}

class User implements IUser
{
 public function __construct( $id ) { }
public function getName()
 {
  return "Jack";
 }
}
class UserFactory
{
 public static function Create( $id )
 {
  return new User( $id );
 }
}
$uo = UserFactory::Create( 1 );
echo( $uo->getName()."\n" );
?>

% php factory1.php 
Jack
%

<?php
interface IUser
{
 function getName();
}

class User implements IUser
{
 public static function Load( $id ) 
 {
    return new User( $id );
 }
public static function Create( ) 
 {
    return new User( null );
 }
public function __construct( $id ) { }
public function getName()
 {
  return "Jack";
 }
}
$uo = User::Load( 1 );
echo( $uo->getName()."\n" );
?>

% php factory2.php 
Jack
%

<?php
require_once("DB.php");

class DatabaseConnection
{
 public static function get()
 {
  static $db = null;
  if ( $db == null )
   $db = new DatabaseConnection();
  return $db;
 }
private $_handle = null;
private function __construct()
 {
  $dsn = 'mysql://root:password@localhost/photos';
  $this->_handle =& DB::Connect( $dsn, array() );
 }
public function handle()
 {
  return $this->_handle;
 }
}
print( "Handle = ".DatabaseConnection::get()->handle()."\n" );
print( "Handle = ".DatabaseConnection::get()->handle()."\n" );
?>

% php singleton.php 
Handle = Object id #3
Handle = Object id #3
%

<?php
interface IObserver
{
 function onChanged( $sender, $args );
}

interface IObservable
{
 function addObserver( $observer );
}
class UserList implements IObservable
{
 private $_observers = array();
public function addCustomer( $name )
 {
  foreach( $this->_observers as $obs )
   $obs->onChanged( $this, $name );
 }
public function addObserver( $observer )
 {
  $this->_observers []= $observer;
 }
}
class UserListLogger implements IObserver
{
 public function onChanged( $sender, $args )
 {
  echo( "'$args' added to user list\n" );
 }
}
$ul = new UserList();
$ul->addObserver( new UserListLogger() );
$ul->addCustomer( "Jack" );
?>

% php observer.php 
'Jack' added to user list
%

<?php
interface ICommand
{
 function onCommand( $name, $args );
}

class CommandChain
{
 private $_commands = array();
public function addCommand( $cmd )
 {
  $this->_commands []= $cmd;
 }
public function runCommand( $name, $args )
 {
  foreach( $this->_commands as $cmd )
  {
   if ( $cmd->onCommand( $name, $args ) )
    return;
  }
 }
}
class UserCommand implements ICommand
{
 public function onCommand( $name, $args )
 {
  if ( $name != 'addUser' ) return false;
  echo( "UserCommand handling 'addUser'\n" );
  return true;
 }
}
class MailCommand implements ICommand
{
 public function onCommand( $name, $args )
 {
  if ( $name != 'mail' ) return false;
  echo( "MailCommand handling 'mail'\n" );
  return true;
 }
}
$cc = new CommandChain();
$cc->addCommand( new UserCommand() );
$cc->addCommand( new MailCommand() );
$cc->runCommand( 'addUser', null );
$cc->runCommand( 'mail', null );
?>

% php chain.php 
UserCommand handling 'addUser'
MailCommand handling 'mail'
%

<?php
interface IStrategy
{
 function filter( $record );
}

class FindAfterStrategy implements IStrategy
{
 private $_name;
public function __construct( $name )
 {
  $this->_name = $name;
 }
public function filter( $record )
 {
  return strcmp( $this->_name, $record ) <= 0;
 }
}
class RandomStrategy implements IStrategy
{
 public function filter( $record )
 {
  return rand( 0, 1 ) >= 0.5;
 }
}
class UserList
{
 private $_list = array();
public function __construct( $names )
 {
  if ( $names != null )
  {
   foreach( $names as $name )
   {
    $this->_list []= $name;
   }
  }
 }
public function add( $name )
 {
  $this->_list []= $name;
 }
public function find( $filter )
 {
  $recs = array();
  foreach( $this->_list as $user )
  {
   if ( $filter->filter( $user ) )
    $recs []= $user;
  }
  return $recs;
 }
}
$ul = new UserList( array( "Andy", "Jack", "Lori", "Megan" ) );
$f1 = $ul->find( new FindAfterStrategy( "J" ) );
print_r( $f1 );
$f2 = $ul->find( new RandomStrategy() );
print_r( $f2 );
?>

% php strategy.php 
Array
(
  [0] => Jack
  [1] => Lori
  [2] => Megan
)
Array
(
  [0] => Andy
  [1] => Megan
)
%