PHP我的注册信息不是将数据发送到数据库

Question

My code is not sending data to the database but it lets me have my own error like DB error or something. tried check my database it seems to be perfect. in the post method the register is the name of the button

<?php
        if(isset($_POST['register']))
        {
            @$username=$_POST['username'];
            @$password=$_POST['password'];
            @$cpassword=$_POST['cpassword'];
            @$role=$_POST['role'];

            if($password==$cpassword)
            {
                $query = "SELECT * FROM usersample WHERE username='$username'";
                //echo $query;
            $query_run = mysqli_query($con,$query);
            //echo mysql_num_rows($query_run);
            if($query_run)
                {
                    if(mysqli_num_rows($query_run)>0)
                    {
                        echo '<script type="text/javascript">alert("This Username Already exists.. Please try another username!")</script>';
                    }
                    else
                    {
                        $query = "INSERT INTO usersample(username,password,role)" ." values('$username','$password','$role')";
                        $query_run = mysqli_query($con,$query);
                        if($query_run)
                        {
                            echo '<script type="text/javascript">alert("User Registered.. Welcome")</script>';
                            $_SESSION['username'] = $username;
                            $_SESSION['password'] = $password;
                            header( "Location: index.php");
                        }
                        else
                        {
                            echo '<p class="bg-danger msg-block">Registration Unsuccessful due to server error. Please try later</p>';
                        }
                    }
                }
                else
                {
                    echo '<script type="text/javascript">alert("DB error")</script>';
                }
            }
            else
            {
                echo '<script type="text/javascript">alert("Password and Confirm Password do not match")</script>';
            }

        }
        else
        {
        }
    ?>

This is my dbconnect and i already doublechecked everything and it seems there's not mistake in my code dbconnect.php

    <?php 
$hostname = "localhost";
$username = "root";
$password = "";
$database = "fransdemo";

$con = new mysqli($hostname, $username, $password) or die ("connection failed");
if (!$con) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>