parallel-download.php

<?php

$files = array(
    'node-v0.6.18.tar.gz' => 'http://nodejs.org/dist/v0.6.18/node-v0.6.18.tar.gz',
    'php-5.4.3.tar.gz' => 'http://it.php.net/get/php-5.4.3.tar.gz/from/this/mirror',
);

function reader($loc) {
    if ($f = fopen($loc, 'r')) {
        stream_set_blocking($f, 0);
        while ($line = fgets($f)) {
            yield $line;
        }
        fclose($f);
    } else {
        throw new \InvalidArgumentException("Invalid location [$loc]");
    }
}

function writer($loc) {
    if ($f = fopen($loc, 'w')) {
        stream_set_blocking($f, 0);
        while (true) {
            $line = yield;
            fwrite($f, $line);
        }
        fclose($f);
    } else {
        throw new \InvalidArgumentException("Invalid location [$loc]");
    }
}

function process_files(array $files) {
    foreach ($files as $file => $url) {
        writer($file)->send(reader($url));
        yield $file;
    }
}

function file_status($seconds) {
    while (true) {
        $file = yield;
        if (file_exists($file)) {
            sleep($seconds * 1000);
            $mbytes = filesize($file) / (1024^2);
            $formatted = number_format($mbytes, 3);
            yield "$file: $formatted MiB" . PHP_EOL;
        }
    }
    yield "Finished downloading $file" . PHP_EOL;
}

foreach (process_files($files) as $file) {
    echo file_status(5)->send($file);
}