<?php

trait GatewayTrait {
	public function __call($name, $arguments) {
		call_user_func_array([$this->repo, $name], $arguments);
	}
}

class Gateway {
	use GatewayTrait;

	public function __construct() {
		$this->repo = new Repo;
	}
}

class Repo {
	public function save($id, $arguments) {
		var_dump($arguments);
	}
}

$gateway = new Gateway;
$gateway->save(13,['foo'=>'bar']);

?>