PHP User Identification Guide

1. the function session_id()

session_start();
$userId = session_id();
echo $userId;

1. the cookie variable

if(isset($_COOKIE['userId'])) {
    $userId = $_COOKIE['userId'];
} else {
    $userId = uniqid(); // 生成唯一标识符
    setcookie('userId', $userId, time() + 3600 * 24 * 30); // 设置Cookie有效期为30天
}

echo $userId;

1. By using IP address and user agent information, a relatively unique identifier can be created by combining the user’s IP address and browser user agent information.

$userId = md5($_SERVER['REMOTE_ADDR'] . $_SERVER['HTTP_USER_AGENT']);
echo $userId;

It is important to note that the methods mentioned above are not foolproof identifiers and can be tampered with by users through modifying or deleting cookies, changing user agent information, etc. Therefore, for sensitive user identification information, it is recommended to implement additional security measures to ensure the uniqueness of the user.