Laravel choosing a class at runtime - php

Question

I am trying to merge two websites created using Laravel 5 into one multisite (yes, I wasn't that experienced when making that decision). The two websites are one for cats and one for dogs.
My problem is that I have a model called Item, the one in cats is storing things in a different table than model Item in dogs.
What I have done in my controller:
protected $posts_class;
public function __construct()
{
$this->items_class = "App\\Models\\" . config('domain') . "\\Item";
}
public function index()
{
$items = $this->items_class::all();
return view('items')->with('items', $items);
}
but it keeps giving an error:
syntax error, unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM)
however if I do:
public function index()
{
$class= $this->items_class;
$items = $class::all();
}
it works.. but I don't want extra variables within the controller method.
I would like to know why the first one doesn't work. If anyone has any recommendations on how to make this multisite work in a better way than this one then I am open to suggestions. Thank you.

Answer 1

The T_PAAMAYIM_NEKUDOTAYIM operator is more commonly known as the Scope Resolution Operator. In the context of PHP, it is used to statically access class methods and variables.
The all() method is a static method on the Eloquent class your model inherits from. As such, it should be called like ClassName::all().
If I understand what you are trying to do correctly, you are trying to use a dynamic variable as the class name. Unfortunately, using $this->someVariable::all() doesn't quite work the way one would expect like that, and as you know, you have to separate it into an individual variable first.
In the spirit of answering your question directly with a way to call it without creating a separate variable, the answer is to use the often forgotten forward_static_call method.
$items = forward_static_call([$this->items_class, 'all']);
If you need to call a static method using this methodology and want to pass an array of parameters, there is also a related function forward_static_call_array().
Reference:
http://php.net/manual/en/language.oop5.paamayim-nekudotayim.php
http://php.net/manual/en/function.forward-static-call.php
http://php.net/manual/en/function.forward-static-call-array.php