我不知道为什么，但它无缘无故地显示错误

Question

<?php
include_once "config.php";
$fname = mysqli_real_escape_string($conn, $_POST['fname']);
$lname = mysqli_real_escape_string($conn, $_POST['lname']);
$email = mysqli_real_escape_string($conn, $_POST['email']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

if(!empty($fname) && !empty($lname) && !empty($email) && !empty($password)){
    // check user email valid or no
    if(filter_var($email, FILTER_VALIDATE_EMAIL));{
        //check email already exist or no
        $sql = mysqli_query($conn, "SELECT email FROM users WHERE email = '{$email}'");
        if(mysqli_num_rows($sql) > 0){
            echo "$email - This email already exists!";
        }else {
            //  check user upload file
            if(isset($_FILES['image'])){
                $img_name = $_FILES['image']['name'];
                $tmp_name = $_FILES['image']['tmp_name'];

                //explode img to get img extension
                $img_explode = explode('.', $img_name);
                $img_ext = end($img_explode);

                $extensions = ['png', 'jpg', 'jpeg', 'gif'];
                if(in_array($img_ext, $extensions) === true){
                    $time = time(); // this will put a time in front of the image
                                    // so that every image will have 
                                    // a unique name
                    // move user uploaded img to folder
                    $new_img_name = $time.$img_name;
                    
                    if(move_uploaded_file($tmp_name, "images/".$new_img_name)){
                        $status = "Active now";
                        $random_id = rand(time(), 10000000);

                        // insert user data to table
                        sql2 = mysqli_query($conn, "INSERT INTO users (unique_id, fname, lname, email, password, img, status);
                                            VALUES ({$random_id}, '{$fname}', '{$lname}', '{$email}', '{$password}', '{$new_img_name}', '{$status}')");
                        if($sql2){
                            $sql3 = mysqli_query($conn, "SELECT * FROM  users WHERE email = '{$email}'");
                            if(mysqli_num_rows($sql3) > 0){
                                $row = mysqli_fetch_assoc($sql3);
                                $_SESSION['unique_id'] = $row['unique_id'];
                                echo "Success!";
                            }
                        }else{
                            echo "Something went wrong!";
                        }
                    }
                }else{
                    echo "Please select an image file - jpg, jpeg, png or gif!"
                }

            }else{
                echo "Please select an image file!"
            }
        }
    }else{
        echo "$email - This is not a valid email!";
    }
}else {
    echo "All input fields are required!";
}
?>

我正在使用此视频作为参考制作实时聊天应用程序 - https://www.youtube.com/watch?v=VnvzxGWiK54 在 signup.php 部分我总是遇到错误怎么办？在我的第一次尝试中，我遇到了愚蠢的错误。这次我的错误较少，但我总是得到这个。请指导