PHP 8.1 Fibers: Suspending and Resuming Work

Fibers introduced in PHP 8.1 provide explicit suspension and resumption of a function call stack.

The examples below begin with the core behavior, then move to an application-oriented use.

How PHP 8.1 Fibers: Suspending and Resuming Work Works

Fibers introduced in PHP 8.1 provide explicit suspension and resumption of a function call stack.

Example 1: Basic Usage

This example uses a small input to make the main behavior visible.

<?php

$fiber = new Fiber(function (): void { echo "begin "; Fiber::suspend(); echo "end"; });
$fiber->start();
$fiber->resume();

Output:

begin end

Fibers introduced in PHP 8.1 provide explicit suspension and resumption of a function call stack.

Example 2: A Different Input

A different set of values shows the same operation in another situation.

<?php

$fiber = new Fiber(function (): string { $value = Fiber::suspend("waiting"); return strtoupper($value); });
echo $fiber->start();
$fiber->resume("ready");
echo $fiber->getReturn();

Output:

waitingREADY

A fiber must be suspended before resume() and has no automatic scheduler; blocking I/O remains blocking.

Practical Example: Applying the Feature

This example shows an application-style use of the feature, with its surrounding setup visible.

<?php

$fiber = new Fiber(function (): string { $response = Fiber::suspend("Need a value"); return "Got: " . $response; });
echo $fiber->start() . "\n";
$fiber->resume("approved");
echo $fiber->getReturn();

Output:

Need a value
Got: approved

The code is shown for learning. Adjust the class names, inputs and error handling to suit your application.

Important Behavior and Edge Cases

• A fiber must be suspended before resume() and has no automatic scheduler; blocking I/O remains blocking.
• Fibers introduced in PHP 8.1 provide explicit suspension and resumption of a function call stack.
• Observe differences in empty inputs, invalid states and optional extension availability where relevant.

Comparison With Related Approaches

Common Beginner Mistakes

Key Takeaways

• Fibers introduced in PHP 8.1 provide explicit suspension and resumption of a function call stack.
• A fiber must be suspended before resume() and has no automatic scheduler; blocking I/O remains blocking.
• Use the example that matches the values, runtime version and dependencies in your application.

PHP 8.1 Fibers: Suspending and Resuming Work is useful when its behavior matches the data structure and lifecycle of your PHP application. Choose it with a clear understanding of its preconditions and returned values.