Using Fibers for Async-Like Workflows

Fibers let a PHP callable suspend and resume execution cooperatively.

The examples focus on the operation itself, including the important distinction: Generators yield values during iteration; Fibers suspend execution at arbitrary points.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Before You Start

Read the input requirements before applying this pattern to production data.

Example 1: Basic Use

A Fiber suspends cooperatively; the application must call resume itself.

<?php
$fiber = new Fiber(static function (): string {
    $payload = Fiber::suspend("waiting");
    return "resumed:" . $payload;
});
$first = $fiber->start();
$fiber->resume('new');
echo $first . " / " . $fiber->getReturn();

Output from a successful local PHP 8.4 run:

waiting / resumed:new

Example 2: Checking Behavior

A Fiber suspends cooperatively; the application must call resume itself.

<?php
$fiber = new Fiber(static function (): string {
    $payload = Fiber::suspend("waiting");
    return "resumed:" . $payload;
});
$first = $fiber->start();
$fiber->resume('ready');
echo $first . " / " . $fiber->getReturn();

Output from a successful local PHP 8.4 run:

waiting / resumed:ready

Example 3: Practical Example

A Fiber suspends cooperatively; the application must call resume itself.

<?php
$fiber = new Fiber(static function (): string {
    $payload = Fiber::suspend("waiting");
    return "resumed:" . $payload;
});
$first = $fiber->start();
$fiber->resume('done');
echo $first . " / " . $fiber->getReturn();

Output from a successful local PHP 8.4 run:

waiting / resumed:done

Important Behavior and Edge Cases

Fibers do not independently schedule I/O or provide threads; a scheduler is required for useful concurrency.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Fibers let a PHP callable suspend and resume execution cooperatively.
• Fibers do not independently schedule I/O or provide threads; a scheduler is required for useful concurrency.
• Generators yield values during iteration; Fibers suspend execution at arbitrary points.

Use Using Fibers for Async-Like Workflows when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.