php 连接数据库 和 form表单简单注册

    header("Content-Type: text/html;charset=utf-8");
    $conn=mysqli_connect("localhost:3306","root","root","mydb") or die("连接失败");



?>

    include("conn.php");

    if (mysqli_connect_errno($conn))
    {
        echo "连接 MySQL 失败: " . mysqli_connect_error();
    }


    if(!empty($_POST['sub'])){
        $username=$_POST['username'];
        $password=$_POST['password'];
        echo  $sql="insert into weblog(username,password) values('$username','$password')";
        mysqli_query($conn,"$sql");

        echo "注册成功";

    }


?>
<form action="add.php" method="POST" >
    账号：<input type="text" name="username"><br>
    密码：<input type="password" name="password"><br>
    <input type="submit" name="sub" value="注册">
form>