Quick Start

Quick Start

This walkthrough builds your understanding one step at a time: two tasks taking turns, what happens without yielding, pausing a task, and getting a value back from a task. Each block is a complete script — prepend these two lines:

require_once 'vendor/autoload.php';

use InitPHP\FiberLoops\Loop;

1. Run two tasks that take turns

You add work with defer() and run it with run(). Inside a task, next() hands control back to the loop so other tasks can advance.

$loop = new Loop();

$loop->defer(function () use ($loop) {
    foreach (['a', 'b', 'c'] as $step) {
        echo "task-1: $step\n";
        $loop->next();
    }
});

$loop->defer(function () use ($loop) {
    foreach (['x', 'y', 'z'] as $step) {
        echo "task-2: $step\n";
        $loop->next();
    }
});

$loop->run();

task-1: a
task-2: x
task-1: b
task-2: y
task-1: c
task-2: z

Each task prints one line, yields, and the loop moves on to the other. They interleave one step at a time.

2. See what next() actually does

next() is the only reason the tasks interleave. Take it out and the first task runs to the end before the second one even starts:

$loop = new Loop();

$loop->defer(function () {
    foreach (['a', 'b', 'c'] as $step) {
        echo "task-1: $step\n";       // no next() — runs straight through
    }
});

$loop->defer(function () {
    foreach (['x', 'y', 'z'] as $step) {
        echo "task-2: $step\n";
    }
});

$loop->run();

task-1: a
task-1: b
task-1: c
task-2: x
task-2: y
task-2: z

This is the heart of cooperative scheduling: the loop never interrupts a task — the task decides when to step aside. (More in Core Concepts.)

3. Pause a task with sleep()

sleep() steps a task aside for a while without freezing the others:

$loop = new Loop();

$loop->defer(function () use ($loop) {
    $loop->sleep(0.2);
    foreach (range(0, 5) as $value) {
        echo $value . PHP_EOL;
    }
});

$loop->defer(function () use ($loop) {
    foreach (range(6, 9) as $value) {
        echo $value . PHP_EOL;
    }
});

$loop->run();

6
7
8
9
0
1
2
3
4
5

The second task finishes first because the first one is sleeping. Note that sleep() is a busy-wait, not an OS sleep — see Yielding & Sleeping.

4. Get a value back with await()

await() runs a task to completion and returns its value:

$loop = new Loop();

$user = $loop->await(function () use ($loop) {
    $loop->next();                  // imagine some I/O happening here
    return ['id' => 42, 'name' => 'Ada'];
});

echo "user: {$user['id']} / {$user['name']}\n";

user: 42 / Ada

Called from inside a task, await() lets the loop's other tasks keep running while it waits — see Awaiting Results.

Where to go next

• Core Concepts — the scheduling model in full.
• Deferring & Running Tasks — defer() and run() in depth.
• Recipes — producer/consumer, graceful shutdown, collecting results, and more.