if语句中没有看到$ _GET变量

Question

我已经使用 GET 将一个变量传递给了一个新页面，并希望将该值插入到我的数据库的表中，但是它表示未定义的变量 $ exex 。我试图在“提交”中回应它。如果声明，但也没有在那里看到。它只回显isset GET if语句中的变量。

以下是代码：

<?php

session_start();
include "includes/connec.inc.php";

if (isset($_GET['exid'])){
    $exex=$_GET['exid'];
}


 $sql = "SELECT id FROM eaouser WHERE email = '" . $_SESSION['email'] . "'";
$result = mysqli_query($conn,$sql);
$row = mysqli_fetch_array($result);
$eaofid=$row['id'];


if (isset($_POST['submit'])){
    if (isset($_POST['feedbacks'])){
        $feedback = $_POST['feedbacks'];
        if (!empty($feedback)){

            $INSERT = "INSERT Into feedback (exfid,eaofid,comment) values(?,?,?)";
                $stmt = $conn->prepare($INSERT);
                $stmt->bind_param("iis", $exex, $eaofid,  $feedback);
                $stmt->execute();
                if ($stmt==TRUE){
                echo "<script> alert('Feedback sent!');
                window.location='feedback.php'
                    </script>";
            }else{
                echo "<script> alert('Error sending feedback!');
                window.location='feedback.php'
                    </script>";
            }

        }else{
                echo "<script> alert('Feedback form is empty!');
                window.location='feedback.php'
                    </script>";
        }
    }
}

HTML：

<div class="panel-body">
                <form method="POST" action="feedback.php">
                    <div class="form-group">
                        <label for="message-text" class="col-form-label">Comment on the experiment:</label>
                        <textarea class="form-control" name="feedbacks" cols="142" rows="5" placeholder="Type here..."></textarea>
                        <br>
                        <button type="submit" name="submit" class="btn" style="background-color: purple;color: white">Send feedback</button>
                    </div>
                </form>

        </div>