MVC Validation Advice - php

Question

I'm currently validating input and returning errors in a "fat controller" as follows:
class SomeController
{
public function register()
{
// validate input
$username = isset($_POST['username']) && strlen($_POST['username']) <= 20 ? $_POST['username'] : null;
// proceed if validation passed
if (isset($username)) {
$user = $this->model->build('user');
if ($user->insert($username)) {
$_SESSION['success'] = 'User created!';
} else {
$_SESSION['error'] = 'Could not register user.';
}
} else {
$_SESSION['failed']['username'] = 'Your username cannot be greater than 20 characters.';
}
// load appropriate view here
}
}
class SomeModel
{
public function insert($username)
{
// sql for insertion
// ...
return $result;
}
}
While this works and is easy enough for me to implement, I understand that this is incorrect because the validation belongs in the model, which I'm attempting to correct using a "fat model" as follows:
class SomeController
{
public function register()
{
$user = $this->model->build('user');
$user->insert($_POST['username']);
// load appropriate view here
// ...
}
}
class SomeModel
{
public function insert($username)
{
// validate input
$error = false;
$username = trim($username) != '' && strlen($username) <= 20 ? $username : null;
// proceed if validation passed
if (isset($username)) {
// sql for insertion
// ...
$_SESSION['success'] = 'User created!';
} else {
// store error in session
$error = true;
$_SESSION['error']['username'] = 'Your username cannot be greater than 20 characters ';
}
return $error ? false : true;
}
}
The problem I see here is that the model is supposed to be portable, in that it should never need to change. But if the requirement for the length of $username changes, then obviously I'll have to alter my model.
I feel like this may be a really common question but I've yet to find a straight-forward answer. Without implementing any extra "layers", "mappers" or whatever other confusing terms are out there, how could the example pseudo-code provided be modified to correctly handle this transaction? (eg, validate input, return error if validation fails)?

Answer 1

Without implementing any extra "layers", "mappers" or whatever
You should consider the "model" to be a application layer rather than a single class. The term "layer" could be thought of as a simple way to reference the M slice of MVC sandwich. So to accomplish the flexibility you desire you will need to create it.
A number of clear seperations can be made. I would consider having three abstractions: services, data mappers and entities.
A service would be exposed to the controller and perform the service being requested.
// some controller
function register() {
$service = $this->getUserService();
$user = $service->register($_POST['first_name'], $_POST['last_name']);
if ($user instanceof \My\Entity\User) {
// set user in view
} else {
// redirect to error
}
}
So task one complete, the controller is now dumb to whatever happens within register, all it wants to know is how to resolve the appropriate result. If there is a user object, success, otherwise false something went wrong.
The service class itself would encapsulate the services being offered:
// class UserService.php
function register($firstname, $lastname) {
// validate arguments
if ($this->isValidUsername(....
$userMapper = $this->getUserMapper();
$user = new My\Entity\User();
$user->setFirstName($firstname);
$user->setLastName($lastname);
return $userMapper->save($user);
}
return false;
}
We handle the validation of the arguments and also create the new user, passing it to the data mapper which will perform the "actual save" abstracting the database operations.
// UserMapper
function save($user) {
// save $user to db
$sql = 'INSERT INTO ....
return true;
}

Answer 2

I'm not sure what you would consider to be an undesirable "layer" or "mapper". This is an interesting question, and my first though was that you could just include a configuration file that defined a constant for your username length. My second though was that you could have someModel extend a class or implement an interface, wherein you values would be set as properties or constants. I suspect that you have thought of these, and are avoiding them; that this is what you mean by avoiding "layers" and "mappers" It seems that you are being guided by these principals in this code:
Avoid "magic numbers"
KISS
Composition over inheritance
skinny controller/fat model
So, are you running php5.4+ ? Maybe define a trait which could be used in this and other models that defines the username length and other changeable values in the application. Or maybe that too is to much of a "layer"?