注意:未定义的索引:页面没有帮助注册 - Notice: Undefined index: page nothing helps register

Notice: Undefined index: page nothing helps register

我知道有几个线程这个问题，但直到现在没有改变。我的代码看起来像这样:

<div data-role="page" id="RegisterPage">
  <div data-role="header">
        <h1>Register</h1>
      </div>
  <div data-role="content">
  <?php
  if(!isset($_GET["page"])){
  ?>
  <form action="register.php?page=2" method="post">
    Username:<input type="text" name="user" placeholder="Username" /><br />
    Password:<input type="text" name="password" placeholder="Password" /><br />
    Repeat Password:<input type="text" name="pw2" placeholder="Repeat Password" /><br />
    <input type="submit" value="Submit" />
</form>
<?php
  }
  if(!isset($_GET["page"])){
      if($_GET["page"] == "2") {
          $user = strtolower($_POST["user"]);
          $pw = md5($_POST["pw"]);
          $pw2 = md5($_POST["pw2"]);
          if($pw != $pw2 ){
              echo $pw;
              echo " The Passwords are diffrent! Please try again..<a href='"register.php '">Back</a>";
          }
      }
  }
  ?>

当我在表单中输入任何东西时，代码将我发送到一个只显示Header的页面。什么也没发生。

也许我什么都看不见，但我就是找不到问题所在。

这是完整的更正代码:

<div data-role="page" id="RegisterPage">
      <div data-role="header">
            <h1>Register</h1>
          </div>
      <div data-role="content">
      <?php
      if(!isset($_GET["page"])){
      ?>
      <form action="register.php?page=2" method="post">
        Username:<input type="text" name="user" placeholder="Username" /><br />
        Password:<input type="text" name="password" placeholder="Password" /><br />
        Repeat Password:<input type="text" name="pw2" placeholder="Repeat Password" /><br />
        <input type="submit" value="Submit" />
    </form>
    <?php
      }
      if(isset($_GET["page"])){ //error was here with !isset(). you did that 2 times
          if($_GET["page"] == "2") {
              $user = strtolower($_POST["user"]);
              $pw = md5($_POST["pw"]);
              $pw2 = md5($_POST["pw2"]);
              if($pw != $pw2 ){
                  echo $pw;
                  echo " The Passwords are diffrent! Please try again..<a href='"register.php '">Back</a>";
              }
          }
      }
      ?>

修复错误:

if(isset($_GET["page"])){  // error in this line
      if($_GET["page"] == "2") {
          $user = strtolower($_POST["user"]);
          $pw = md5($_POST["pw"]);
          $pw2 = md5($_POST["pw2"]);
          if($pw != $pw2 ){
              echo $pw;
              echo " The Passwords are diffrent! Please try again..<a href='"register.php '">Back</a>";
          }
      }
  }

if(isset($_GET["page"]))代替if(!isset($_GET["page"]))