Check and/or set button state mvc php - php

Question

I am new to php/mvc and experimenting with a small website.
I would like to change to state of a button depending on a select query. It's a simple 'favourite' toggle button. The query will look to the 'favourite' table of my db for the 'isFav' field (0 or 1).
I would like the button colour to be green (btn-success) if the query finds a result (1), and the colour to be default (btn-default) if not (0).
Should be simply but I can't seem to get it. I think I am getting confused regarding passing of the variables between my view and model.
My books_model.php code is as follows
class BooksModel
{
public function isFav()
{
$book_id = $_GET['id']; // from url
$user_id=$_SESSION['user_id'];
$sql = "SELECT isFav FROM favourite WHERE book_id = :book_id AND user_id = :user_id AND isFav = 1";
$query = $this->db->prepare($sql);
$query->bindParam(':book_id', $book_id);
$query->bindParam(':user_id', $user_id);
$query->execute();
if ($query->rowCount() == 1) {
$css = 'btn-success';
echo $css; //for testing
} else {
$css = 'btn-default';
echo $css; // for testing
}
}
}
My books.php controller is as follows;
class Books extends Controller
{
function itemView()
{
$itemView_model = $this->loadModel('Books');
$this->view->books = $itemView_model->itemView();
$this->view->render('books/itemView');
$itemView_model->isFav();
}
}
My itemView.php html button code is as follows;
echo '<button class="btn '.$css.'"></button>';
The only thing printed on the page is a btn-success or btn-default (top left). This toggles whenever I click the button. Therefore I assume my query is working.
Apologies for the code I am a newbie and I do appreciate any help offered, even a point in the right direction.

Answer 1

Try this:
public function isFav() {
(...)
if ($query->rowCount() == 1) {
$css = 'btn-success';
echo $css; //for testing
} else {
$css = 'btn-default';
echo $css; // for testing
}
return $css;
}
And in your View:
echo "<button class=\"btn ".$itemView_model->isFav()."\"></button>";
The reason: Your Variable $css in your isFav() method is not known in your view (the scope of the variable is the isFav() method).
This line:
$itemView_model->isFav();
Requests the return value of this function, so, clearly, the value bust be returned in order to be available.
The reason you see the seemingly correct answer printed is that the echo call is in the same scope as the $css variable.