class factory{  function __construct($name){    if(file_exists('./'.$name.'.class.php')){      return new $name;    }else{      die('not exist');    }  }}

class instance{  public $val = 10;  private static $instance ;  private function __construct(){}  private function __clone(){}  //設置為靜態方法才可被類調用  public static function getInstance(){    /*if(!isset(self::$instance)){      self::$instance = new self;    }*/    if(!isset(instance::$instance)){      instance::$instance = new self;    }    return instance::$instance;  }}$obj_one = instance::getInstance();$obj_one->val = 20;//clone可以調用__clone()克隆即new出一個新的的對象//$obj_two = clone $obj_one;$obj_two = instance::getInstance();echo $obj_two->val;echo '<p>';var_dump($obj_one,$obj_two);

20object(instance)[1] public 'val' => int 20object(instance)[1] public 'val' => int 20

class mysqldb{  private $arr = array(    'port' => 3306,    'host' => 'localhost',    'username' => 'root',    'passward' => 'root',    'dbname' => 'instance',    'charset' => 'utf8'     );  private $link;  static $instance;  private function __clone(){}  private function __construct(){    $this->link = mysql_connect($this->arr['host'],$this->arr['username'],$this->arr['passward']) or die(mysql_error());    mysql_select_db($this->arr['dbname']) or die('db error');    mysql_set_charset($this->arr['charset']);  }  static public function getInsance(){    if(!isset(mysqldb::$instance)){      mysqldb::$instance = new self;    }    return mysqldb::$instance;  }  public function query($sql){    if($res = mysql_query($sql)){      return $res;    }return false;  }  //fetch one  public function get_one($sql){    $res = $this->query($sql);    if($result = mysql_fetch_row($res)){      return $result[0];    }  }  //fetch row  public function get_row($sql){    $res = $this->query($sql);    if($result = mysql_fetch_assoc($res)){      return $result;    }    return false;  }  //fetch all  public function get_all($sql){    $res = $this->query($sql);    $arr = array();    while($result = mysql_fetch_assoc($res)){      $arr[] = $result;    }    return $arr;  }}$mysql = mysqldb::getInsance();