PHP会话的未定义索引

我是 PHP新手,在会话方面更像是初学者.我有我的index.PHP页面,这是用户可以注册和登录的地方.表单分别发布到validate.PHP和loginvalidate.PHP页面,用于注册和登录.

我加载时在index.PHP上有这些错误：

1)注意：未定义的索引：已注册
2)注意：未定义的索引：从未使用过

我试过在很多方面修改我的文本,但我从来没有解决错误.

的index.PHP

<?PHP
            if ($_SESSION['registered'] != NULL){
                echo $_SESSION['registered'];                   
            }
            if ($_SESSION['badlogin'] != NULL){
                echo $_SESSION['badlogin'];
            }
            if ($_SESSION['neverused'] != NULL) {
                echo $_SESSION['neverused'];                    
            }
    ?>

Validate.PHP(提交注册表后)

if (MysqLi_num_rows($result) > 0) {  //IF THERE IS A PASSWORD FOR THAT EMAIL IN DATABASE
    $_SESSION['registered'] = "Email is already registered.";
    MysqLi_close($db_handle);
    header('Location: index.PHP');
    exit();
}

Loginvalidate.PHP(提交登录表单后)

if ($numrows!=0)  //IF THERE IS A PASSWORD FOR THAT EMAIL IN THE DATABASE
{
  if ($row['password'] == $password) {  //IF THE PASSWORD MATCHES USER INPUT
      header('Location: homepage.PHP');
      echo "lol";
      exit();
  }
  else{
    $_SESSION['badlogin'] = "Email/password combination not valid.";
    MysqLi_close($db_handle);
    header('Location: index.PHP');
    exit();
  } 
}
else {  //THERE IS NO PASSWORD FOR THAT EMAIL,SO THAT EMAIL IS NOT REGISTERED
    $_SESSION['neverused'] = "Email is not registered.";
    MysqLi_close($db_handle);
    header('Location: index.PHP');
    exit();
}

好的,所以我的脚本完成了它的目的.我唯一无法解决的是这些会话错误.你有没有看到滥用会话？当然,我已经在所有.PHP文件中启动了会话.

另请注意,我知道没有黑客的保护.这仅适用于未包含任何重要数据的未来原型.

解决方法

这些错误的原因是您正在尝试读取不存在的数组键. isset()功能在那里你可以测试这个.对于每个元素,如下所示的东西将起作用;您不需要空检查,因为您从不为元素指定null：

// check that the 'registered' key exists
if (isset($_SESSION['registered'])) {

    // it does; output the message
    echo $_SESSION['registered'];

    // remove the key so we don't keep outputting the message
    unset($_SESSION['registered']);
}

你也可以在循环中使用它：

$keys = array('registered','badlogin','neverused');

//iterate over the keys to test
foreach($keys as $key) {

    // test if $key exists in the $_SESSION global array
    if (isset($_SESSION[$key])) {

        // it does; output the value
        echo $_SESSION[$key];

        // remove the key so we don't keep outputting the message
        unset($_SESSION[$key]);
    }
}