I tried my code in laravel php to send otp from firebase by phone number , but I get always MISSING_CLIENT_IDENTIFIER in the response , I already activated the phone authentication service in my firebase app ,

    $phone = $request->get('phone');
        $apiKey = 'my key'; 


        try {
            $client = new Client();
            $response =$client>post('https://identitytoolkit.googleapis.com/v1/accounts:sendVerificationCode?key=' . $apiKey, [
                'json' => [
                    'phoneNumber' => "+".$phone           
                ]
            ]);

            $data = json_decode($response->getBody(), true);

the response is

“error”: “Client error: POST https://identitytoolkit.googleapis.com/v1/accounts:sendVerificationCode?key=my key resulted in a 400 Bad Request response:n{n “error”: {n “code”: 400,n “message”: “MISSING_CLIENT_IDENTIFIER”,n “errors”: [n {n “message”: ” (truncated…)n”

I want to send the code and verify the code in another api