php代码在xampp localhost上工作正常，但在实时服务器上不工作

如何解决php代码在xampp localhost上工作正常，但在实时服务器上不工作

我已将所有PHP 文件上传到与本地主机相同的实时服务器上。很少文件可以正常工作。但是，当我尝试注册时，我的注册页面不起作用，该页面未在PHPmyadmin中存储数据。并显示如下错误。 enter image description here

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <Meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <title>Event Management</title>
        <script src="https://code.jquery.com/jquery-3.5.1.js"></script>
        <!--<link href="css/style.css" rel="stylesheet"/>-->
        <link href="layout/styles/layout.css" rel="stylesheet" type="text/css" media="all">
        <!--<link href="css/bootstrap.css" rel="stylesheet"/>-->
        <link href="css/bootstrap.min.css" rel="stylesheet"/>
        <script src="js/bootstrap.min.js"></script> 
        <script src="js/main.js" type="text/javascript"></script>
    </head>

    <body>
        <!-- Database file include -->
        <?PHP require_once ('main.PHP'); ?>
        <!-- Database file include End -->
        <div class="container justify-content-center">
            <h2 align="center">Log In or Sign Up</h2>
                <div class="container">
                <form method="post" action="main.PHP">
                    <div class="row justify-content-center">
                        <div class="col-6">
                            <input type="text" class="form-control" placeholder="Name" name="name"/>
                            <label></label>
                            <label></label>
                            <input type="text" class="form-control" placeholder="username" name="username"/>
                            <label></label>
                            <label></label>
                            <input type="password" class="form-control" placeholder="password" name="password"/>
                            <label></label>
                            <label></label>
                            <input type="email" class="form-control" placeholder="email" name="email"/>
                            <label></label>
                            <label></label>
                            <input type="text" class="form-control" placeholder="contact" name="contact"/>
                            <label></label>
                            <label></label><br />
                            <button class="btn btn-info" id="register" name="register">Register</button>
                        </div>
                    </div>
                    <div class="row justify-content-center">
                        <div class="col-6">
                            <label>Already have an Account?</label>
                            <a href="login.PHP" style="color:#03F !important;">Login Here.</a>
                        </div>
                    </div>
                </form>
            </div>
        </div>
    </body>
</html>

用于注册的main.PHP 文件代码

if(!empty($_POST['name']) && !empty($_POST['username']) && !empty($_POST['password']) && !empty($_POST['email']) && !empty($_POST['contact']))
{
    $Name = $_POST['name'];
    $uName = $_POST['username'];
    $pass = $_POST['password'];
    $mail = $_POST['email'];
    $contact = $_POST['contact'];
    $date = date('d-m-yy');
    
    $MysqLi->query("insert into register(Name,username,password,Email_Id,Phone_No,date_Created) values('$Name','$uName','$pass','$mail','$contact','$date')") or die($MysqLi->error);
    $MysqLi->query("insert into users(email,user_name,pass_word) select r.Email_Id,r.username,r.password from     register r where r.Email_Id NOT IN (SELECT email FROM users);") or die($MysqLi->error);
    echo "Data inserted successfully!";
    header('location: login.PHP');
}

解决方法

main.php行号73出错。

未定义变量：mysqli

请显示更多以查看并获取您的解决方案。

谢谢