Laravel set global variable for all custom helpers,controllers, and models

i've ever asked this question before in codeigniter, now I want to ask about this in laravel.

I want to set a global variable for custom helpers, models, and controllers the variable is got from database result..

Here is the example:

don't know where to put the variable

 $data= DB::table('categories')->where('id', '2')->first();
 $this->product_var = $data->product;  **//main global variable**

custom helper

function test() {
    if($this->product_var=="product name") {

    }
}

my controller

function index() {
    echo $this->product_var;
}

my model

function get_data() {
     echo $this->product_var;
}

As you can see my scripts above, $this->product_var is almost used for custom helper, my controller, and my model. in codeigniter we create Globals.php in libraries folder, or just put the variable in core controllers. Where should i set the global variable?