PHP - 错误HTTP 500 - 当我尝试连接到mysql数据库时

Question

当我尝试连接到数据库时，我得到错误http 500我试过它在本地数据库上它工作正常，当我在网上上传没有工作

如果我改变我的localhost 我有三个错误

1-http 500

用户

的2连接失败访问被拒绝

3连接失败无法找到mysql主机

如果有人可以提供帮助

谢谢

<?php
$Server = "localhost";
 $Username = "username";
 $PW = "password";
 $DB = "database";
$u=filter_input(INPUT_POST, 'Username');
$p=filter_input(INPUT_POST, 'Password');
$con = mysqli_connect($Server, $Username, $PW, $DB);

 if($con == false) {
     die("Error: " . mysqli_error_connect());
 }  

$st=$con->prepare("SELECT * FROM user WHERE username = ? ");
$st->bind_param('s', $u);
$st->execute();
$rs=$st->get_result();
if ($rs->num_rows > 0) {
while ($row = $rs->fetch_assoc()) 
    {


     if ($u===$row["username"]&&$p===$row["password"])
    {
        echo "hi";



    }
        else 
            {
                 echo "Wrong username or password";

            }
    }     



} else {
    echo "wrong username or password";
}



 mysqli_close($connection);
 ?>