为什么PHP会话本身看起来是空的

我正在建立一个网站，我有2个页面，一个用于登录，一个用于上传文件

当用户登录时，我将从数据库中获取的该用户的ID设置到

$\u SESSION

变量中，当用户转到第二个页面时，他可以上传一个文件，并将对该文件的引用和ID存储到数据库中

我的前端btw位于完全不同的域中，因此当用户上载文件时，

$\u SESSION

变量将为空，我如何解决

PHP检查example.com上的登录页面

<?php 
session_start();

if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
}

$a = headers_list();

require "Connessione.php";

$connessione = new Connessione();
$ris = $connessione->getUtente($_POST['id']);

if($risposta['esisteGia'])
{
    $_SESSION['ID'] = $ris[0]['IDUtente'];
    $_SESSION['Tipo'] = $ris[0]['Ruolo'];
}


echo json_encode($risposta);
?>

const esisteGia = () => {
    async function controllaCheEsistaGia() {
      let udid = "123";
      let data = new FormData();
      data.append("id", udid);
      let risposta = await fetch(
        "https://example.com/checkLogin.php",
        {
          method: "POST",
          body: data,
          credentials: "include"
        }
      );

      risposta = await risposta.json();
      console.log(risposta);
    }

    controllaCheEsistaGia();
  };

session_start();
if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
}

if(!isset($_SESSION['ID'])). //Here the session is now empty again
{
    header("Location: {$_SERVER['HTTP_ORIGIN']}/Login");
    die();
}
header('Content-Type: application/json; charset=utf-8');


$filePDF = $_FILES['pdfDaCaricare']['tmp_name']; //Also the $_FILES is not set, and I don't know why

此时将设置

$\u会话

example.com上的uploadFile.php

<?php 
session_start();

if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
}

$a = headers_list();

require "Connessione.php";

$connessione = new Connessione();
$ris = $connessione->getUtente($_POST['id']);

if($risposta['esisteGia'])
{
    $_SESSION['ID'] = $ris[0]['IDUtente'];
    $_SESSION['Tipo'] = $ris[0]['Ruolo'];
}


echo json_encode($risposta);
?>

const esisteGia = () => {
    async function controllaCheEsistaGia() {
      let udid = "123";
      let data = new FormData();
      data.append("id", udid);
      let risposta = await fetch(
        "https://example.com/checkLogin.php",
        {
          method: "POST",
          body: data,
          credentials: "include"
        }
      );

      risposta = await risposta.json();
      console.log(risposta);
    }

    controllaCheEsistaGia();
  };

session_start();
if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');
    header('Access-Control-Max-Age: 86400');    // cache for 1 day
}

if(!isset($_SESSION['ID'])). //Here the session is now empty again
{
    header("Location: {$_SERVER['HTTP_ORIGIN']}/Login");
    die();
}
header('Content-Type: application/json; charset=utf-8');


$filePDF = $_FILES['pdfDaCaricare']['tmp_name']; //Also the $_FILES is not set, and I don't know why

example2.com/uploadFile

const caricaFile = async e => {
    const fd = new FormData();
    fd.append("pdfDaCaricare", file);


    await axios.post(
      "example.com/uploadFile.php"
      fd,
      {
        method: "POST",
        credentials: "include",
        headers: {
          "content-type": "multipart/form-data"
        },
        onUploadProgress: function(progressEvent) {
          let percentCompleted = Math.round(
            (progressEvent.loaded * 100) / progressEvent.total
          );
          document.getElementById("percentuale").innerText = percentCompleted;
        }
      }
    );
  };

---

即使在localhost中，这也不起作用

会话Cookie仅适用于一个域，因此甚至可能会出现会话问题

---

可能使用不同的方法来验证您的用户。

我的前端btw位于完全不同的域上，这意味着什么。你是说你登录到一个域并从另一个域上传吗？#决不要使用key

['ID']

进行sessionRiggsFolly：我的后端php文件在一个域上，而HTML、CSS和JS文件在另一个域上。泽利卡：这可能是问题所在吗？@DavideVitiello将其更改为

['myId']

或其他任何内容，您将看到：）@DavideVitiello抱歉，我刚刚在PHP7.3上测试了它，并且它与

['ID']

一起工作，所以这可能不是问题。但通常建议您在会话中定义自己的自定义密钥。并始终选中

isset&！空

并且无法将会话cookie从一个域传递到另一个域？对于子域，通过会话cookie在同一域后面传递其他资源。您可以通过某个存储在后端共享会话，然后通过url或其他方式传递会话id来尝试还原会话。不知道为什么有些人开始否决我的答案，似乎他们不明白。检查你的会话cookie，了解它创建了什么域。可能这篇文章还验证了会话cookie值是否在php中，以便可以恢复会话