Is it possible to export the code of the main loop as a function, so that there is no need to write a callback function.

[pixelvm]

PHP does not have async/wait syntax. Is it possible to add a function to call the main loop code so that we can write synchronous code instead of callback functions.

<?php

class Loop {
    function loopTick () {
        // ...
    }

    function run () {
        while (loopTick()) {}
    }
}

// function wait run the function loopTick likely $loop->run(), and block the current thread until promise settled.
function waitPromiseSettled ($promise) {
    $rejected = false;
    $resolved = false;
    $error = null;
    $ret = null;
    $promsie->then(function ($val) use (&$resolved, &$ret) {
        $ret = $val;
        $resolved = true;
    })->catch(function ($err) use (&$rejected, &$error) {
        $error = $err;
        $rejected = true;
    });
    while (loopTick()) {
        if ($resolved) {
            return $ret;
        } else if ($rejected) {
            throw $error;
        }
    }
    throw new Exception("...");
}

class Promise {
    function resolve () {
        // ...
    }

    function reject () {
        // ...
    }

    function wait () {
        return waitPromiseSettled($this);
    }
}

// coding sync 
$value = new Promise(function (/* ... */) { /* ... */ })->wait();

[clue]

@pixelvm Excellent question!

This is indeed supported via clue/reactphp-block. For example, this can be used to await a pending HTTP request that is otherwise exposed as a promise like this:

use Clue\React\Block;

$loop = React\EventLoop\Factory::create();
$browser = new React\Http\Browser($loop);

$promise = $browser->get('http://example.com/');

try {
    $response = Block\await($promise, $loop);
    // response successfully received
} catch (Exception $e) {
    // an error occured while performing the request
}

See also https://github.com/reactphp/http#blocking

I hope this helps 👍