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PHP uses redis as cache (efficient technology)

高效PHP Redis缓存技术,可参考下步骤

是否想过PHP使用redis作为缓存时,如何能:

● 前后台模块共用Model层;

● 但是,不能每个Model类都进行缓存,这样太浪费Redis资源;

● 前后台模块可以自由决定从数据库还是从缓存读数据;

● 没有冗余代码;

● 使用方便。

● 这里我们先展示实现的最终效果。

最终的代码和使用说明请移步Github:

https://github.com/yeszao/php-redis-cache。

马上安装使用命令:

$ composer install yeszao/cache

 

经过简单配置就可以使用,请参看Github的README说明。

1 最终效果

假设在MVC框架中,model层有一个Book类和一个getById方法,如下:

class Book
{
    public function getById($id)
    {
        return $id;
    }
}

 

加入缓存技术之后,原来方法的调用方式和返回的数据结构都不应该改变。

所以,我们希望,最后的效果应该是这样的:

(new Book)->getById(100);           // 原始的、不用缓存的调用方式,还是原来的方式,一般是读取数据库的数据。
(new Book)->getByIdCache(100);      // 使用缓存的调用方式,缓存键名为:app_models_book:getbyid: + md5(参数列表)
(new Book)->getByIdClear(100);      // 删除这个缓存
(new Book)->getByIdFlush();         // 删除 getById() 方法对应的所有缓存,即删除 app_models_book:getbyid:*。这个方法不需要参数。

 

这样我们可以很清楚的明白自己在做什么,同时又知道数据的来源函数,并且被引用方式完全统一,可谓一箭三雕。

其实实现起来也比较简单,就是使用PHP的魔术方法__call()方法。

2 __call()方法

这里简单说明一下__call方法的作用。

在PHP中,当我们访问一个不存在的类方法时,就会调用这个类的__call()方法。

(如果类方法不存在,又没有写__call()方法,PHP会直接报错)

假设我们有一个Book类:

class Book
{
    public function __call($name, $arguments)
    {
        echo '类Book不存在方法', $name, PHP_EOL;
    }

    public function getById($id)
    {
        echo '我的ID是', $id, PHP_EOL;
    }
}

 

当调用存在的getById(50)方法时,程序打印:我的ID是50。

而如果调用不存在的getAge()方法时,程序就会执行到A类的__call()方法里面,这里会打印:类Book不存在方法getAge。

这就是__call的原理。

3 实现细节

接下来我们就利用__call()方法的这种特性,来实现缓存策略。

从上面的例子,我们看到,__call()方法被调用时,会传入两个参数。

name:想要调用的方法名arguments:参数列表

我们就可以在参数上面做文章。

还是以Book类为例,我们假设其原本结构如下:

class Book
{
    public function __call($name, $arguments)
    {
        // 待填充内容
    }

    public function getById($id)
    {
        return ['id' => $id, 'title' => 'PHP缓存技术' . $id];
    }
}

 

开始之前,我们还确认Redis的连接,这是缓存必须用到的,这里我们写个简单的单例类:

class Common
{
    private static $redis = null;

    public static function redis()
    {
        if (self::$redis === null) {
            self::$redis = new \Redis('127.0.0.1');
            self::$redis->connect('redis');
        }
        return self::$redis;
}

 

然后,我们开始填充__call()方法代码,具体说明请看注释:

class Book
{
    public function __call($name, $arguments)
    {
        // 因为我们主要是根据方法名的后缀决定具体操作,
        // 所以如果传入的 $name 长度小于5,可以直接报错
        if (strlen($name) < 5) {
            exit(&#39;Method does not exist.&#39;);
        }

        // 接着,我们截取 $name,获取原方法和要执行的动作,
        // 是cache、clear还是flush,这里我们取了个巧,动作
        // 的名称都是5个字符,这样截取就非常高效。
        $method = substr($name, 0, -5);
        $action = substr($name, -5);

        // 当前调用的类名称,包括命名空间的名称
        $class = get_class();

        // 生成缓存键名,$arguments稍后再加上
        $key = sprintf(&#39;%s:%s:&#39;, str_replace(&#39;\\&#39;, &#39;_&#39;, $class), $method);
        // 都用小写好看点
        $key = strtolower($key);

        switch ($action) {
            case &#39;Cache&#39;:
                // 缓存键名加上$arguments
                $key = $key . md5(json_encode($arguments));

                // 从Redis中读取数据
                $data = Common::redis()->get($key);

                // 如果Redis中有数据
                if ($data !== false) {
                    $decodeData = json_decode($data, JSON_UNESCAPED_UNICODE);
                    // 如果不是JSON格式的数据,直接返回,否则返回json解析后的数据
                    return $decodeData === null ? $data : $decodeData;
                }

                // 如果Redis中没有数据则继续往下执行

                // 如果原方法不存在
                if (method_exists($this, $method) === false) {
                    exit(&#39;Method does not exist.&#39;);
                }

                // 调用原方法获取数据
                $data = call_user_func_array([$this, $method], $arguments);

                // 保存数据到Redis中以便下次使用
                Common::redis()->set($key, json_encode($data), 3600);

                // 结束执行并返回数据
                return $data;
                break;

            case &#39;Clear&#39;:
                // 缓存键名加上$arguments
                $key = $key . md5(json_encode($arguments));
                return Common::redis()->del($key);
                break;

            case &#39;Flush&#39;:
                $key = $key . &#39;*&#39;;

                // 获取所有符合 $class:$method:* 规则的缓存键名 
                $keys = Common::redis()->keys($key);
                return Common::redis()->del($keys);
                break;

            default:
                exit(&#39;Method does not exist.&#39;);
        }
    }

    // 其他方法
}

 

这样就实现了我们开始时的效果。

4 实际使用时

在实际使用中,我们需要做一些改变,把这一段代码归入一个类中,

然后在model层的基类中引用这个类,再传入Redis句柄、类对象、方法名和参数,

这样可以降低代码的耦合,使用起来也更灵活。

完整的代码已经放在Github上,请参考文章开头的参考地址。

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