qlg.tsgz.moe/vendor/swoole/examples/coroutine/fwrite.php

<?php
use Swoole\Coroutine as co;

$fp = fopen(__DIR__ . "/test.data", "a+");

co::create(function () use ($fp)
{
    $r =  co::fwrite($fp, "hello world\n", 5);
    var_dump($r);
});