为什么会出现此错误？：“字段列表”中的未知列“名字”

Question

  if(isset($_POST["submit"]))
  {

    // Details for inserting into the database

        $id = htmlentities($_POST["id"]);
        $firstname = htmlspecialchars($_POST["firstname"]);
        $lastname = htmlspecialchars($_POST["lastname"]);
        $username = htmlspecialchars($_POST["username"]);
        $password = htmlspecialchars($_POST["password"]);

    // Dealing with inserting 

        $query = "INSERT INTO `myDatabaseForAll`.`users` (`id`, `firstname`, `lastname`, `username`, `password`)
                 VALUES (NULL, $firstname, $lastname,$username,$password)";
        $result = mysqli_query($connection,$query);


        if(!$result) {
            die('There were some errors '.mysqli_error($connection));
        } else {
            redirect_to('index.php');
        }

}

Answer 1

$query = "INSERT INTO `myDatabaseForAll`.`users` (`id`, `firstname`, `lastname`, `username`, `password`)
         VALUES (NULL, $firstname, $lastname,$username,$password)";

you need single quote around text feilds in sql queries

change above query to

$query = "INSERT INTO `myDatabaseForAll`.`users` (`id`, `firstname`, `lastname`, `username`, `password`)
         VALUES (NULL, '$firstname', '$lastname','$username','$password')";

Answer 2

This error can be occurred due to mismatch of table column name with the name you have given in the query. If it is not the case please try the below code.

$query = "INSERT INTO `myDatabaseForAll`.`users` (id, firstname, lastname, username, password)
         VALUES (NULL, '".$firstname."', '".$lastname."','".$username."','".$password."')";

In your query you are concatenating some string parts with php variables. So this concatenation should be done in the above way using the concatenating operator.