在AJAX调用成功后创建PHP会话变量

function sendData() {
    var xhr = new XMLHttpRequest();
    xhr.open('POST', 'set_session.php', true);
    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4 && xhr.status === 200) {
            console.log('Session variable set successfully');
        }
    };
    xhr.send('data=someValue');
}

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $data = $_POST['data'] ?? '';
    $_SESSION['my_session_var'] = $data;
    echo 'Session variable set';
} else {
    http_response_code(405); // Method Not Allowed
    echo 'Method Not Allowed';
}
?>

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: POST");
header("Access-Control-Allow-Headers: Content-Type");