How API handles data caching and paging in PHP

With the popularity of the Internet and the acceleration of digitalization, the use of APIs is becoming more and more common, especially in web applications. In PHP, caching and paging are two important technical issues for large or complex APIs. In this article, we will discuss in detail how the API handles data caching and paging in PHP.

1. Application of data cache

1. Definition of data cache

Data cache is an optimization technology that can store data in memory , to improve reading speed and response time. Compared with reading data from disk or database, data caching can effectively reduce the number of requests to the back-end storage system, thereby improving API performance.

2. How to implement data caching

(1) Use static variables

In PHP, defining a static variable of a class can be used to store data cache. For example, the following code snippet demonstrates how to use static variables to implement data caching:

class Cache {
  private static $data = [];

  public static function get($key) {
    if (isset(self::$data[$key])) {
      return self::$data[$key];
    }
    return null;
  }

  public static function set($key, $value) {
    self::$data[$key] = $value;
  }
}

// 从缓存中获取数据
$data = Cache::get('my_key');
if (!$data) {
  // 如果缓存中没有数据，从数据库中获取
  $data = Data::getFromDb();
  // 将数据写入缓存
  Cache::set('my_key', $data);
}

(2) Using Memcached

Memcached is a high-performance, distributed memory object caching system. It can cache data in memory to improve the speed and performance of data access. In PHP, the Memcached extension library provides the Memcached class, which can easily access the Memcached cache system. The following is a sample code that uses Memcached to implement data caching:

// 实例化一个Memcached对象
$memcached = new Memcached();
// 添加一台Memcached服务器
$memcached->addServer('127.0.0.1', 11211);

// 尝试从缓存中获取数据
$data = $memcached->get('my_key');
if (!$data) {
  // 如果缓存中没有数据，从数据库中获取
  $data = Data::getFromDb();
  // 将数据写入缓存，过期时间为10分钟
  $memcached->set('my_key', $data, 600);
}

2. Application of paging technology

1. Definition of paging technology

Paging refers to Divide the data collection into multiple pages for display, with a certain amount of data displayed on each page. In web applications, paging technology can divide large amounts of data into multiple pages to facilitate user viewing and navigation.

2. How to implement paging technology

(1) Use LIMIT and OFFSET

In SQL, LIMIT and OFFSET can be used to limit the number of returned records Quantity and offset. For example, the following SQL statement can be used to get the 11th to 20th records:

SELECT * FROM table_name LIMIT 10 OFFSET 10;

In PHP, the values ​​of LIMIT and OFFSET can be calculated based on the current page number and the number of records displayed on each page, and then used to Get data from database. The following is a sample code:

// 获取当前页码和每页记录数量
$page = isset($_GET['page']) ? (int)$_GET['page'] : 1;
$limit = isset($_GET['limit']) ? (int)$_GET['limit'] : 10;

// 计算LIMIT和OFFSET的值
$offset = ($page - 1) * $limit;

// 从数据库中获取数据
$data = Data::getFromDb($limit, $offset);

(2) Using Cursor

Using Cursor technology is an advanced paging technology, which can reduce the cost of querying the database while improving the efficiency of data access. You can use Cursor to store the status of query results in the database, and then use this status to obtain the next page of data. The following is a sample code:

// 获取当前状态（如果没有状态，则为null）
$cursor = isset($_GET['cursor']) ? $_GET['cursor'] : null;

// 从数据库中获取下一页数据
$data = Data::getFromDb($limit, $cursor);

// 获取下一个状态
$nextCursor = Data::getNextCursor($cursor, $limit);

// 输出数据和下一个状态
$output = [
  'data' => $data,
  'next_cursor' => $nextCursor,
];
echo json_encode($output);

The above two methods can be selected and used according to actual needs to achieve data caching and paging and improve API performance and response speed.

Summary

In PHP, data caching and paging are two very important technical issues. Using data caching technology can store data in memory, thereby improving API performance and response speed; using paging technology can improve data access efficiency and reduce the cost of querying the database. These two technologies can be freely chosen and used according to actual needs to meet the needs of web applications.

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