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This article mainly introduces "how to understand that Session in PHP may cause concurrency problems". In daily operation, I believe many people have doubts about how to understand Session in PHP may cause concurrency problems. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubt that "how to understand Session in PHP may cause concurrency problems"! Next, please follow the editor to study!

When developing Web applications, people often use Session to store data. However, some people may not know that in PHP, improper use of Session can cause concurrency problems. Kishan Gor, a senior engineer at Plus91 Technologies, an Indian provider of software solutions for the medical industry, explained the issue on a personal blog.

If the same client sends multiple requests concurrently, and each request uses Session, the existence of an PHP Session lock causes the server to respond to those requests serially rather than in parallel. This is because by default, PHP uses files to store Session data. For each new Session,PHP, a file is created and data is continuously written to it. Therefore, each time the session_start () method is called, the Session file is opened and the exclusive lock of the file is obtained. In this way, if the server script is processing a request and the client sends another request that also requires Session, the latter request will block until the previous request processing finishes releasing the exclusive lock on the file. However, this is limited to multiple requests from the same client, that is, requests from one client do not block requests from another client.

If the script is short, this is usually fine. But if the script takes a long time to run, it can cause problems. In modern Web application development, it is very common to use AJAX technology to send multiple requests to get data in the same page. If these requests need to use Session, the first request will acquire the Session lock when it arrives at the server, the other requests will have to wait, and all requests will be processed serially, even if they are not dependent on each other. This will greatly increase the response time of the page.

One way to avoid this problem is to call the session_write_close () method to close the Session immediately after using the Session. The Session lock is released, even if the current script is still waiting to be processed. It is important to note that after this method is called, the current script cannot further manipulate Session.

In particular, the problems and views presented in this article apply only to the PHP default Session management mode that uses the session_start () method. For example, a user pointed out that the problem of DynamoDB,Session locking would not occur if the application was hosted on AWS EC2 and properly configured.

At this point, the study on "how to understand that Session in PHP may cause concurrency problems" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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