我的MYSQL代码没有运行

Question

function UpdateTable(){

global $connection;

$username = $_POST['username'];
$password = $_POST['password'];
$id = $_POST['id'];

    $query="UPDATE users SET ";
    $query .="username = '$username' , ";
    $query .="password = '$password' ";
    $query .="WHERE id = $id ";

    $result = mysqli_query($connection, $query);

    if(!$result){

        die("Database connection failed ".mysqli_error($connection));
    }

}

这是我收到的错误消息：

  

数据库连接失败您的SQL语法出错;校验   与您的MariaDB服务器版本对应的手册   正确的语法使用近＆＃39;＆＃39;在第1行