结构性模式：享元模式

享元模式的设计思想是尽量复用已创建的对象，常用于工厂方法内部的优化
因此，享元模式就是通过工厂方法创建对象，在工厂方法内部，很可能返回缓存的实例，而不是新创建实例，从而实现不可变实例的复用

class student{
    public $id;
    public $name;
    private $redis;
    
    public function __construct($id, $name){
        $this->id = $id;
        $this->name = $name;
        
        $redis = new \Redis();
        $redis->connect('127.0.0.1', 6379);
        $this->redis = $redis;
    }

    public function create(){
        $cacheKey = 'student' . $this->id;
        $tmpGet = $this->redis->get($cacheKey);
        if(!$tmpGet){
            echo 'create new student' . PHP_EOL;
            $student = new student($this->id, $this->name);
            $this->redis->set($cacheKey, serialize($student));
        }else{
            echo 'from cache' . PHP_EOL;
            $student = unserialize($tmpGet);
            echo $student->id . ' name is : ' . $student->name;
        }
        
        return $student;
    }
    
}

$obj = new student(1, 'tom');
$result = $obj->create();