Using Redis caching technology in PHP to optimize database reading and writing

With the continuous development of Internet technology, the amount of data is getting larger and larger, and the pressure of reading and writing databases is also increasing. However, our user experience needs to maintain extremely fast response at all times. At this time, caching technology becomes important. Particularly important. This article will introduce how to use Redis caching technology to optimize database reading and writing of PHP applications.

1. What is Redis?

Redis is simply a key-value storage system. Unlike other key-value storage systems, Redis supports data storage of multiple data types (strings, lists, sets, ordered sets, hash tables) and provides a rich set of operation commands. Redis is an in-memory storage database that also supports data persistence to disk and can completely replace the traditional cache system.

2. Why use Redis?

The flow of a conventional application is usually that the application reads data from the database and then presents the data to the user in some form. In this process, the most time-consuming thing is reading data from the database. The Redis cache can help us cache part of the data into the memory, so that repeated reads can be obtained directly from the cache, avoiding frequent queries to the database, reducing the pressure on the database, improving reading and writing efficiency, and thus reducing the system cost. response time and improve the overall throughput of the system.

3. How to use Redis in PHP applications?

Before using Redis, we need to install Redis first. The Redis installation and PHP extension installation process will not be detailed here. We assume that readers already have installed Redis and PHP extensions. Next we introduce how to use Redis in PHP applications.

1. Data Cache

In the application, you can set and obtain cached data through the Redis set and get commands.

//设置缓存
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);  //连接到Redis
$redis->set('name', 'redis cache'); //设置缓存
$redis->expire('name', 3600);       //设置过期时间

//获取缓存
$redis = new Redis();
$redis->connect('127.0.0.1', 6379); //连接到Redis
$name = $redis->get('name');         //获取缓存
if($name){                           //判断缓存是否存在
    echo $name;
}else{                               //不存在则从数据库中读取数据
    $name = 'get data from database';
    $redis->set('name', $name);
    $redis->expire('name', 3600);
    echo $name;
}

In the above code, we first determine whether there is cache data in Redis. If there is, get it directly. If not, get it from the database, set the cache and set the expiration time.

2. Batch operation of cached data

Sometimes we need to cache multiple pieces of data at one time. Redis's multi and exec commands allow us to batch operate cached data.

//批量设置缓存
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$redis->multi();
$redis->set('name1', 'cache1');
$redis->set('name2', 'cache2');
$redis->set('name3', 'cache3');
$redis->exec();

//批量获取缓存
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$redis->multi();
$redis->get('name1');
$redis->get('name2');
$redis->get('name3');
$result = $redis->exec();

In the above code, we can use the multi and exec commands to perform multiple operations of setting the cache or obtaining multiple caches.

3. Cache read and write separation

In applications, some data operations are frequent and do not require high data integrity, such as login status, etc. You can consider storing these data Cache to Redis, and more critical data such as username, password, email, etc. can be stored in the database. The advantage of this is to improve reading and writing efficiency, and will not cause database data inconsistency due to changes in cached data.

//缓存数据
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$redis->set('login:userid', '1');       //将登录状态存储到Redis中
$redis->expire('login:userid', 3600);

//读取数据
//先从Redis中读取
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$loginUserId = $redis->get('login:userid');
//如果Redis中不存在，则从数据库中读取
if(empty($loginUserId)){
    $sql = "select id from user where username='admin'";
    $result = $mysqli->query($sql)->fetch_assoc();
    $loginUserId = $result['id'];
    //将读取到的数据存储到Redis缓存中
    $redis->set('login:userid', $loginUserId);
    $redis->expire('login:userid', 3600);
}

In the above code, we store the user login status in Redis. When reading, first read it from the Redis cache. If it does not exist in Redis, read it from the database.

4. Summary

Using Redis caching technology can greatly improve the read and write performance of PHP applications, achieve decoupling between applications and databases, reduce system response time, and improve user experience. . When using Redis cache, you need to pay attention to the order of writing and reading, and set the validity period of cached data according to the actual situation. It should be noted that in situations of high concurrency, distribution, cache avalanche, etc., corresponding operation and maintenance technologies and methods need to be combined to ensure the stability and reliability of the cache system.

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