composer require amphp/amp

async looping

<?php 
require_once __DIR__ . '/vendor/autoload.php';

use Amp\Delayed;
use Amp\Loop;
use function Amp\asyncCall as u;

list($counter, $delay) = [10, 2000];
u(function () use ($counter, $delay) {
    for ($i = 1; $i <= $counter; $i++) {
        printf(">> %s" . PHP_EOL, $i);
        yield new Delayed($delay);
    }
});

Loop::run();