在PHP中使用IF-ELSE回显Javascript

我是新来PHP的，我有一个问题，我的Javascript现在不工作

这是我到目前为止的代码

    <?php

        $email = $_POST["App_Email"];
        $password = $_POST["App_Password"];
        $name = $_POST["App_Name"];
        $lName = $_POST["App_LName"];
        $gender = $_POST["App_Gender"];
        $birthday = $_POST["App_Birthday"];
        $nationality = $_POST["App_Nationality"];
        $telNumber = $_POST["App_Tel"];
        $address = $_POST["App_Address"];
        $district = $_POST["App_District"];
        $city = $_POST["App_City"];
        $zipcode = $_POST["App_Zipcode"];

        $repass = $_POST["RePassword"];

        $message = "";
        if($email == ""  or $password == "" or $repass == "" or $name == "" or $lName == "" or $birthday == "" or $nationality == "" or $telNumber == "" or $address == "" or $district == "" or $city == "" or $zipcode == "" ){
            $message = "FILL ALL";
        }
        elseif($repass != $password){
            $message = "NOT MATCH"; 
        }

    echo '<script type="text/javascript">';


    if($message == "FILL ALL"){
        echo 'alert("Please fill in all provided field(s).")';
        echo 'location.href = "registration.php"';
        return;
    }
    else if($message == "NOT MATCH"){
        echo 'alert("Your confirmation password is not match with your password.")';
        echo 'location.href = "registration.php"';
        return;
    }


echo '</script>';

?>

<br><br>

<form method="POST" action="confirm-registration.php">

Name : <?php echo $_POST["App_Name"]; ?><br><br>
Lastname : <?php echo $_POST["App_LName"]; ?><br><br>
Gender :  <?php echo $_POST["App_Gender"]; ?><br><br>
Date of birth : <?php echo $_POST["App_Birthday"]; ?> <br><br>
Nationality : <?php echo $_POST["App_Nationality"]; ?><br><br>
Tel. : <?php echo $_POST["App_Tel"]; ?><br><br>
Address : <?php echo $_POST["App_Address"]; ?><br><br>
District : <?php echo $_POST["App_District"]; ?><br><br>
City : <?php echo $_POST["App_City"]; ?><br><br>
Zipcode : <?php echo $_POST["App_Zipcode"]; ?><br><br>

<input type='hidden' name='App_Email' value='<?=$email?>'>
<input type='hidden' name='App_Password' value='<?=$password?>'>
<input type='hidden' name='App_Name' value='<?=$name?>'>
<input type='hidden' name='App_LName' value='<?=$lName?>'>
<input type='hidden' name='App_Gender' value='<?=$gender?>'>
<input type='hidden' name='App_Birthday' value='<?=$birthday?>'>
<input type='hidden' name='App_Nationality' value='<?=$nationality?>'>
<input type='hidden' name='App_Tel' value='<?=$telNumber?>'>
<input type='hidden' name='App_Address' value='<?=$address?>'>
<input type='hidden' name='App_District' value='<?=$district?>'>
<input type='hidden' name='App_City' value='<?=$city?>'>
<input type='hidden' name='App_Zipcode' value='<?=$zipcode?>'>

<button onClick="history.back()";> Back </button>  <input type="submit" name="submit" value="Confirm">
</form>

---

代码中的各种问题：

缺少
isset（）
。打开错误报告，您将发现大量
注意：未定义索引
错误

为什么
在
中返回
？它是一个函数吗

缺少
在Javascript中：

if($message == "FILL ALL"){
    echo 'alert("Please fill in all provided field(s).");';
    echo 'location.href = "registration.php";';

}
else if($message == "NOT MATCH"){
    echo 'alert("Your confirmation password is not match with your password.");';
    echo 'location.href = "registration.php";';
}


所有HTML字段都是隐藏的，用户在哪里输入值

使用；内部回音语句

if($message == "FILL ALL"){
  echo 'alert("Please fill in all provided field(s).");';
  echo 'location.href = "registration.php";';
}
else if($message == "NOT MATCH"){
   echo 'alert("Your confirmation password is not match with your password.");';
   echo 'location.href = "registration.php";';
}

为什么
返回
中的
如果
？你知道
返回的目的，不是吗？因为（4）它来自最后一页。我没有发布我的密码