How to determine if the user is online in php

There are many ways to determine whether a user is offline or online. Here is a relatively simple and commonly used logic.

Ideas:

1: First get the user’s last saved session_id (recommended Learning: PHP programming from entry to proficiency)

//这里可以保存到数据库中获取
//假设
$memberSessionId = getMemberSessionId();

2: Use the session_id obtained in the first step to find whether the current session exists

//只要开启了session_start() ; 那么每个用户只要打开你的网站都将分配一个session_id
/* 这段代码可以获取到你服务器上的所有session
$handle = opendir(session_save_path());
while (false !== ($file = readdir($handle))) {
if(!in_array($file, array('.', '..', 'session_dir')))
echo "$file<br />";
}
closedir($handle);
*/
//这一步要获取到你在服务器上和用户匹配的session
// 假设
$serverSession == $memberSessionId // 如果存在,则在线,否则反之

Three: If the user exits normally, delete the current session

// 将全局SESSION变量数组设置空.
$_SESSION = array();
// 如果SESSION数据存储在COOKIE中则删除COOKIE.
// Note: 将注销整个SESSION对象, 而不仅仅是SESSION数据!
if (isset($_COOKIE[session_name()])) {
setcookie(session_name(), '', time()-42000, '/');
}
// 最后，注销SEESION.
session_destroy();

Four, if the user closes the browser directly, wait for the server session to be recycled

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