amp-observer.php

<?php

use Amp\Artax\Response;
use Rx\Observable;
use Amp\Artax\Client;

Amp\execute(function () {

    $sitesObs = Observable::defer(function () {
        return Observable::fromPromise((new Client)->request('https://google.com'));
    })->retryWhen(function (Observable $errors) {
        return $errors->take(3)->delay(1000);
    });

    //Every 1 second make the
    $codesObs = Observable::interval(1000)
        ->flatMapTo($sitesObs)
        ->map(function (Response $response) {
            return $response->getStatus();
        })
        ->take(3)
        ->toArray()
        ->map('json_encode');

    echo yield $codesObs->toPromise();

});