当一个对象包含复杂单独立的，必须基于判决执行的功能性的若干部分时，最佳的方法是适用基于委托设计模式的对象。 7xRHTML5中文学习网 - HTML5先行者学习网

<?php    
    /**  
     * 示例： Web站点具有创建MP3文件播放列表的功能， 也具有选择以 M3U 或 PLS 格式下载播放列表的功能。  
     * 以下代码示例展示常规与委托两种模式实现  
     */   
    //常规实现    
    class Playlist {   
           
        private $_songs;    
           
        public function __construct() {   
            $this->_songs = array();   
        }   
           
        public function addSong($location, $title) {   
            $song = array("location" => $location, "title" => $title);   
            $this->_songs[] = $song;   
        }   
           
        public function getM3U() {   
            $m3u = "#EXTM3U/n/n";   
               
            foreach ($this->_songs as $song) {   
                $m3u .= "#EXTINF: -1, {$song['title']}/n";   
                $m3u .= "{$song['location']}/n";   
            }   
               
            return $m3u;   
        }   
           
        public function getPLS() {   
            $pls = "[playlist]]/nNumberOfEntries = ". count($this->_songs) . "/n/n";   
               
            foreach ($this->_songs as $songCount => $song) {   
                $counter = $songCount + 1;   
                $pls .= "File{$counter} = {$song['location']}/n";   
                $pls .= "Title{$counter} = {$song['title']}/n";   
                $pls .= "LengthP{$counter} = -1 /n/n";   
            }   
               
            return $pls;   
        }   
    }   
       
    $playlist = new Playlist();   
       
    $playlist->addSong("/home/aaron/music/brr.mp3", "Brr");   
    $playlist->addSong("/home/aaron/music/goodbye.mp3", "Goodbye");   
       
    $externalRetrievedType = "pls";   
       
    if ($externalRetrievedType == "pls") {   
        $playlistContent =  $playlist->getPLS();   
    } else {   
        $playlistContent =  $playlist->getM3U();   
    }   
       
    echo $playlistContent;   
       
    //委托模式实现    
    class newPlaylist {   
       
        private $_songs;   
        private $_tyepObject;   
       
        public function __construct($type) {   
            $this->_songs = array();   
            $object = "{$type}Playlist";   
            $this->_tyepObject = new $object;   
        }      
           
        public function addSong($location, $title) {   
            $song = array("location" => $location, "title" => $title);   
            $this->_songs[] = $song;   
        }   
           
        public function getPlaylist() {   
            $playlist = $this->_tyepObject->getPlaylist($this->_songs);   
            return $playlist;   
        }   
    }   
       
    class m3uPlaylist {   
        public function getPlaylist($songs) {   
            $m3u = "#EXTM3U/n/n";   
               
            foreach ($songs as $song) {   
                $m3u .= "#EXTINF: -1, {$song['title']}/n";   
                $m3u .= "{$song['location']}/n";   
            }   
               
            return $m3u;   
        }      
    }   
       
    class plsPlaylist {   
        public function getPlaylist($songs) {   
            $pls = "[playlist]]/nNumberOfEntries = ". count($songs) . "/n/n";   
               
            foreach ($songs as $songCount => $song) {   
                $counter = $songCount + 1;   
                $pls .= "File{$counter} = {$song['location']}/n";   
                $pls .= "Title{$counter} = {$song['title']}/n";   
                $pls .= "LengthP{$counter} = -1 /n/n";   
            }   
               
            return $pls;   
        }   
    }   
       
    $externalRetrievedType = "pls";   
    $playlist = new newPlaylist($externalRetrievedType);   
       
    $playlist->addSong("/home/aaron/music/brr.mp3", "Brr");   
    $playlist->addSong("/home/aaron/music/goodbye.mp3", "Goodbye");   
       
    $playlistContent = $playlist->getPlaylist();   
    echo $playlistContent;   
 ?> 

 数据库脚本请参照：http://www.cxybl.com/html/wlbc/Php/2011_1126_9458.html7xRHTML5中文学习网 - HTML5先行者学习网