php mysql 中文跟数据库对比不成功

用户名如果用中文，无法正常登陆成功，英文没有问题。
mysql内无乱码
<?php
//插入连接数据库的相关信息
require_once 'config.php';

//开启一个会话
if (!session_id()) session_start();

$error_msg = "";
//如果用户未登录，即未设置$_SESSION['user_id']时，执行以下代码
if(!isset($_SESSION['user_id'])){
if(isset($_POST['submit'])){//用户提交登录表单时执行如下代码
$dbc = mysqli_connect(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);
$user_username = mysqli_real_escape_string($dbc,trim($_POST['username']));
$user_password = mysqli_real_escape_string($dbc,trim($_POST['password']));

if(!empty($user_username)&&!empty($user_password)){
//MySql中的SHA()函数用于对字符串进行单向加密
$query = "SELECT id, name FROM admin_user WHERE name = '$user_username' AND "."pass = SHA('$user_password')";
//用用户名和密码进行查询
$data = mysqli_query($dbc,$query);
//若查到的记录正好为一条，则设置SESSION，同时进行页面重定向
if(mysqli_num_rows($data)==1){
$addlogin = "update admin_user set logincount = logincount+1 where name = '$user_username';";
$row = mysqli_fetch_array($data);
$_SESSION['user_id']=$row['id'];
$_SESSION['username']=$row['name'];
mysqli_query($dbc,$addlogin);
$home_url = 'index.php';
header('Location: '.$home_url);
}else{//若查到的记录不对，则设置错误信息
$error_msg = $user_username.', Sorry, you must enter a valid username and password to log in.';
}
}else{
$error_msg = $user_username.', Sorry, you must enter a valid username and password to log in.';
}
}
}else{//如果用户已经登录，则直接跳转到已经登录页面
$home_url = 'index.php';
header('Location: '.$home_url);
}
?>