缓存的使用，缓存使用_PHP教程

    /**
     * Memcache缓存类
     */
    define('CACHE_HOST', '127.0.0.1');
    define('CACHE_PORT', 11211);
    
    class Cache{
        private static $instance = null;  
        
        private $_cache = null;  // 缓存操作对象
        
        const prefix = 'APP|';  // 缓存键值的前缀，为该项目名称 
        
        private function __construct(){
            if($this->_cache === null){
                try{
                    $this->_cache = new Memcache;
                    if(!$this->_cache->connect(CACHE_HOST, CACHE_PORT)){
                        exit('connect failed');
                    }
                    
                }
                catch(Exception $e){
                    echo 'ERROR: '.$e->getMessage();
                }
                
            }
        }
        /** 
         * 返回单例
         */
        public static function getInstance(){
            if(self::$instance === null){
                self::$instance = new self();
            }
            return self::$instance;
        }
        /**
         * 生成键名
         */
        private function genKey($key){
            return Cache::prefix.$key;
        }
        
        public function __destruct(){
            if($this->_cache !== null){
                return $this->_cache->close();
            }
        }
        /**
         * 添加元素，设置过期时间
         */
        public function add($key, $val, $expire = 3600){
            return $this->_cache->add($this->genKey($key), $val, 0, $expire);
        }
        /**
         * 重置元素
         */
        public function set($key, $val, $expire = 3600){
            echo 'cache key: '.$this->genKey($key).'
';  // test
            return $this->_cache->set($this->genKey($key), $val, 0, $expire);
        }
        /**
         * 获取元素
         */
        public function get($key){
            return $this->_cache->get($this->genKey($key));
        }
        /**
         * 自增
         */
        public function increment($key, $val = 1){
            return $this->_cache->increment($this->genKey($key), $val);
        }
        /**
         * 自减
         */
        public function decrement($key, $val = 1){
            return $this->_cache->decrement($this->genKey($key), $val);
        }
        /**
         * 删除元素
         */
        public function delete($key, $timeout = 0){
            return $this->_cache->delete($this->genKey($key), $timeout);
        }
        /**
         * 删除所有元素
         */
        public function flush(){
            return $this->_cache->flush();
        }    
    }

    /**
     * 数据库操作
     */
    define('DB_NAME', 'test');
    define('DB_HOST', '127.0.0.1');
    define('DB_PORT', 3306);
    define('DB_USER', 'root');
    define('DB_PASS', '1234');
    
    class Dal{
        private static $instance = null;
        
        public $pdo = null;        
        
        private function __construct(){
            try{
                $dsn = 'mysql:dbname='.DB_NAME.';host='.DB_HOST.':'.DB_PORT;
                $this->pdo = new PDO($dsn, DB_USER, DB_PASS);
            }
            catch(PDOException $e){
                echo 'Error: '.$e->getMessage();
                return false;
            }
        }
        //获取实例
        public static function getInstance(){
            if(self::$instance === null){
                self::$instance = new self();
            }
            return self::$instance;
        }
        // 获取用户信息
        public function getUserInfoByUid($uid){
            $sql = sprintf('select * from tab1 where uid = %s limit 1', $uid);
            $stmt = $this->pdo->query($sql);
            return $stmt->fetch(PDO::FETCH_ASSOC);
        }
    }

    include 'Dal.php';
    include 'Cache.php';
    
    class UserModel{
        private static $instance = null;
        
        public $cache = null;
        
        public $db = null;
        
        // 缓存键名部分，通过函数名称及参数拼接
        const cache_get_userinfo_uid = 'GET|USER|INFO|BY|UID|%s';
        
        private function __construct(){
            // 获取对应类实例
            $this->cache = Cache::getInstance();
            $this->db = Dal::getInstance();
        }
        
        public static function getInstance(){
            if(self::$instance === null){
                self::$instance = new self();
            }
            return self::$instance;
        }
        
        /**
         根据uid获取用户信息
         */
        public function getUserInfoByUid($params, $timeout = 3600){
            // 缺少必要参数uid，返回
            if(empty($params['uid'])){
                return null;
            }
    
            // 拼接缓存键名
            $key = sprintf(self::cache_get_userinfo_uid, $params['uid']);
                    
            // 获取缓存数据
            $data = json_decode($this->cache->get($key), true);
            
            echo 'cache=>
';
            var_dump($data);
            
            // 缓存为空
            if(!$data){
                $data = $this->db->getUserInfoByUid($params['uid']);
                if(empty($data)){
                    return null;
                }
                // 在数据库中获取到数据后，重新写入缓存
                $this->cache->set($key, json_encode($data), $timeout);
            }
            else{
                
            }
            return $data;
        }
    }
    // 测试
    $data = UserModel::getInstance()->getUserInfoByUid(array('uid'=>17653), 5);
    echo 'UserModel=>
';
    var_dump($data);
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