access $variable property in test method

Have been working on this test for a while with help from a previous post.

I'm really happy to get the paymentGateway working after a few days by myself without posting. That was a tough thing to get passing.

Hit a snag here, it's so close but thought someone more experienced can help out.

I know it's a very basic thing, but I've tried using some techniques here: https://www.php.net/manual/en/sdo.sample.getset.php and my favorite error was this one! ErrorException: Indirect modification of overloaded property App\User::$email has no effect

/** @test */
    public function an_authenticated_bidder_can_pay_bidreserve_fee()
    {
        $this->withoutExceptionHandling();

        $user = factory(User::class)->create();
        $job = factory(Job::class)->create();

        $this->actingAs($user);
        // dd($user->email);
        $this->payBidReserve($job, [
            'email' => $user->email,
            'bidreserve' => 500,
            'payment_token' => $this->paymentGateway->getValidTestToken()
        ]);
        // dd($this->paymentGateway->getValidTestToken()); 
                
        // dd($this->response);
        $this->response->assertStatus(201);
        $this->assertCount(1, $job->bidReserves);

        // Make sure customer was charged correct amount
        $this->assertEquals(500, $this->paymentGateway->totalCharges());
    // dd($job);

        // Make sure order exists for customer   
        $bidderEmail = $user->email;  
        // dd($bidderEmail);
        // dd($user->email);  $company->departments[0]

        $order = $job->ordersFor($bidderEmail)->first();
        dd($order);
        $this->assertEquals($user->email, $order->email);
        // dd($order);
        // dd($job->bidReserves);
    }

The $user->email property reliably spits out a faker email such as ... "[email protected]" However, when it's placed as an argument for ordersFor() it returns null. If as shown above I get the property put in a variable it returns ErrorException: Undefined variable: bidderEmail.

Why is that?

//Job.php
    public function ordersFor($bidderEmail)
    {
        return $this->orders()->where('email', $bidderEmail)->get();
    }

thank you ~