Custom WordPress plugins development

I am trying to modify a WordPress plugins and i am stuck on a function, below is the function details

class MyClass
{
public function __construct()
{
add_filter('woocommerce_add_to_cart_validation', array($this, 'check_topup_product_callback'), 10,5);
}

public function check_topup_product_callback(){
another_function(); //call api function
}

function order_process(){
//order will process here
//need to get the "$abc" variable/response here
}
} //class end

another_function(){

//some api response will get here

$abc;
//need to send the response/variable from here
}


kindly check the function and solve the issue