PHP查询数据库登录

$conn = mysqli_connect($hostname_conn, $username_conn, $password_conn,$database_conn)or trigger_error(mysqli_error(),E_USER_ERROR);
$sql = "SELECT * FROM admin where user = '$user' AND pass = '$pass'";
mysqli_query($conn, "set names 'utf8'");//不写这句有可能乱码
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
echo json_encode('1');//将请求结果转换为json格式，微信只能对
}else{
echo json_encode("2");
}