Error: strlen(): Argument #1 ($string) must be of type string, Thenextweb\PassGenerator given

[pascualkoko]

Hello, I am trying to create a pass but I am receiving the error of the title. If I use a dd to see it I receive that error but not using it and trying to do the return I am receiving this error:

Symfony\Component\HttpFoundation\Response::setContent(): Argument #1 ($content) must be of type ?string, Illuminate\Support\Facades\Response given, called in /var/app/current/vendor/laravel/framework/src/Illuminate/Http/Response.php on line 72

I checked it all my identifiers and is all ok so I don't know what's happening. Sorry for my english, I am not a native english speaker. This is my code:

// Start here

public function generateAppleWalletPass(Request $request)
    {
        $validator = Validator::make(['kokoId' => $request->kokoId], [
            'kokoId' => ['required', 'string', 'min:1'],
        ]);
        if ($validator->fails()) {
            abort(404);
        }
        $koko = Koko::find(Hashids::decode($request->kokoId)[0]);
        if (isset($koko)) {
            $pass_identifier = $koko->uid;
            $pass = new PassGenerator($pass_identifier);
            $pass_definition = [
                "description"       => "example",
                "formatVersion"     => 1,
                "organizationName"  => "xxxxxxxxx",
                "passTypeIdentifier" => "pass.com.wallet.xxxxxxx",
                "serialNumber"      => "xxxxxxxxxx",
                "teamIdentifier"    => "xxxxxxxxx",
                "foregroundColor"   => "rgb(99, 99, 99)",
                "backgroundColor"   => "rgb(212, 212, 212)",
                "barcode" => [
                    "message"   => "encodedmessageonQR",
                    "format"    => "PKBarcodeFormatQR",
                    "altText"   => "altextfortheQR",
                    "messageEncoding" => "utf-8",
                ],
                "boardingPass" => [
                    "headerFields" => [
                        [
                            "key" => "destinationDate",
                            "label" => "Trip to: BCN-SANTS",
                            "value" => "15/09/2015"
                        ]
                    ],
                    "primaryFields" => [
                        [
                            "key" => "boardingTime",
                            "label" => "MURCIA",
                            "value" => "13:54",
                            "changeMessage" => "Boarding time has changed to %@"
                        ],
                        [
                            "key" => "destination",
                            "label" => "BCN-SANTS",
                            "value" => "21:09"
                        ]

                    ],
                    "secondaryFields" => [
                        [
                            "key" => "passenger",
                            "label" => "Passenger",
                            "value" => "J.DOE"
                        ],
                        [
                            "key" => "bookingref",
                            "label" => "Booking Reference",
                            "value" => "4ZK6FG"
                        ]
                    ],
                    "auxiliaryFields" => [
                        [
                            "key" => "train",
                            "label" => "Train TALGO",
                            "value" => "00264"
                        ],
                        [
                            "key" => "car",
                            "label" => "Car",
                            "value" => "009"
                        ],
                        [
                            "key" => "seat",
                            "label" => "Seat",
                            "value" => "04A"
                        ],
                        [
                            "key" => "classfront",
                            "label" => "Class",
                            "value" => "Tourist"
                        ]
                    ],
                    "backFields" => [
                        [
                            "key" => "ticketNumber",
                            "label" => "Ticket Number",
                            "value" => "7612800569875"
                        ], [
                            "key" => "passenger-name",
                            "label" => "Passenger",
                            "value" => "John Doe"
                        ], [
                            "key" => "classback",
                            "label" => "Class",
                            "value" => "Tourist"
                        ]
                    ],
                    "locations" => [
                        [
                            "latitude" => 37.97479,
                            "longitude" => -1.131522,
                            "relevantText" => "Departure station"
                        ]
                    ],
                    "transitType" => "PKTransitTypeTrain"
                ],
            ];

            $pass->setPassDefinition($pass_definition);

            $pass->addAsset(public_path('img/qr-logo.png'));

            $pkpass = $pass->create();

            dd($pkpass); // Here is where I am receiving first error

            // Second error down here
            return new Response($pkpass, 200, [
                'Content-Transfer-Encoding' => 'binary',
                'Content-Description' => 'File Transfer',
                'Content-Disposition' => 'attachment; filename="pass.pkpass"',
                'Content-length' => strlen($pkpass),
                'Content-Type' => PassGenerator::getPassMimeType(),
                'Pragma' => 'no-cache',
            ]);
        }
    }