In PHP, how to solve the problem that the first request is empty when using session to cache WeChat access_token?

Optimization strategies for PHP WeChat access_token cache and Session

In PHP development, using Session to cache WeChat access_token often leads to the problem of empty first request. This article analyzes this problem and provides an optimization solution.

Problem description

Access_token is required for WeChat interface calls. Developers often store it in a Session to improve efficiency. However, in actual applications, the token is often not available during the first request, and the second request is normal.

Code examples and problem analysis

The following code snippet shows common errors:

 <?php session_start();

// ...Other codes are omitted...

if (!empty($_SESSION[&#39;access_token&#39;]) && $_SESSION[&#39;expire_time&#39;] > time()) {
    // Use cached access_token
    // ...
} else {
    // Get access_token
    $app_id = 'xxx';
    $app_secret = 'xxx';
    $token_url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={$app_id}&secret={$app_secret}";
    // ... Get token logic...
    $_SESSION['access_token'] = $access_token;
    $_SESSION['expire_time'] = time() 120; // Excessive validity return $_SESSION['access_token'];
}

The problem is:

1. Session is not an ideal access_token cache solution: access_token is valid for 7200 seconds, but only 120 seconds are set in the code, and each user caches it separately, which is inefficient.
2. Logical defect: During the first request, $_SESSION['access_token'] is empty, and you go directly to else block to get the token, but only the token is returned after obtaining it, and no subsequent business logic is executed.

Solution

1. Adopt a more appropriate caching mechanism: use distributed caches such as file cache or Redis, and all users share the same access_token to avoid repeated requests.
2. Improve cache update logic: File cache can be used in cache_time access_token format, updated every 7000 seconds, and use file locks ( flock ) to prevent concurrent conflicts. Shared locks ( LOCK_SH ) are used for reading, and exclusive locks ( LOCK_EX ) are used for writing.
3. Timing Tasks: Use timing tasks (such as crontab) to automatically update access_token every 7000 seconds to ensure that the cache is always valid.
4. Large project recommendations: For high concurrency scenarios, Redis or Memcached is the better choice, and its performance far exceeds file cache.

Best Practices

It is recommended to use timed tasks to regularly update access_token, and combine high-performance cache systems such as Redis or Memcached to achieve efficient and stable access_token management. Avoid using Session to cache access_token directly.

Summarize

By improving the caching mechanism and logic, it can effectively solve the problem of using Session to cache WeChat access_token in PHP, resulting in the first request being empty, and improve application performance and stability.

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