设计模式(21)strategy模式

abstract class Strategy{
  abstract function algorithm();
}
class ConcreteStrategyA extends Strategy{
  function algorithm(){
    echo "ConcreteStrategyA";
  }

}
class ConcreteStrategyB extends Strategy{
  function algorithm(){
    echo "ConcreteStrategyB";
  }

}
class Context{
  private $strategy;
  function __construct($s){
    $this->strategy = $s;
  }
  public function __call($method, $args){
   return call_user_func_array(array($this->strategy, $method), $args);  
  }

}
$concreteStrategyA = new ConcreteStrategyA();
$concreteStrategyB = new ConcreteStrategyB();
$c = new Context($concreteStrategyA);
$c->algorithm();
$c = new Context($concreteStrategyB);
$c->algorithm();