Fibers for concurrency in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new Fiber.

PHP

<?php
$fiber = new \Fiber(function() {
    echo [1];
});
$fiber->start();
?>

Drag options to blanks, or click blank then click option'

A"Hello from Fiber!"

BHello from Fiber!

Cprint("Hello")

Decho 'Hello'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Using print instead of echo inside the Fiber

Passing a non-string value to echo

The Fiber function should echo a string. The string must be quoted properly in PHP.

2fill in blank

medium

Complete the code to start the Fiber and get its return value.

PHP

<?php
$fiber = new \Fiber(function() {
    return 42;
});
$result = $fiber->[1]();
echo $result;
?>

Drag options to blanks, or click blank then click option'

Astart

Brun

Cbegin

Dresume

Attempts:

3 left

💡 Hint

Common Mistakes

Using resume() before start()

Using a non-existent method like run() or begin()

To start a Fiber and get its return value, use the start() method.

3fill in blank

hard

Fix the error in the Fiber code to yield a value and resume it.

PHP

<?php
$fiber = new \Fiber(function() {
    $value = Fiber::[1](10);
    echo "Received: $value";
});
$fiber->start();
$fiber->resume(20);
?>

Drag options to blanks, or click blank then click option'

Apause

Bsuspend

Cyield

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using yield instead of suspend

Using pause or stop which do not exist

The Fiber::suspend() method pauses the Fiber and sends a value outside.

4fill in blank

hard

Fill both blanks to create a Fiber that suspends and resumes with values.

PHP

<?php
$fiber = new \Fiber(function() {
    $value = Fiber::[1]('start');
    echo "Resumed with: $value";
});
$fiber->[2]();
$fiber->resume('resume');
?>

Drag options to blanks, or click blank then click option'

Asuspend

Bstart

Cresume

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using resume() to start the Fiber

Using start() instead of suspend() inside the Fiber

Use Fiber::suspend() to pause and send a value, and start() to begin the Fiber.

5fill in blank

hard

Fill all three blanks to create a Fiber that exchanges values twice.

PHP

<?php
$fiber = new \Fiber(function() {
    $value1 = Fiber::[1]('first');
    echo "Got: $value1\n";
    $value2 = Fiber::[2]('second');
    echo "Got: $value2\n";
    return 'done';
});

$result = $fiber->[3]();
echo "Result: $result";
?>

Drag options to blanks, or click blank then click option'

Asuspend

Bresume

Cstart

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using resume() inside the Fiber instead of suspend()

Using begin() which does not exist

Using resume() to start the Fiber

Inside the Fiber, use suspend() twice to pause and send values. Use start() to begin the Fiber.

Practice

1. What is the main purpose of using Fiber in PHP?

easy

A. To speed up database queries automatically

B. To create permanent background threads

C. To pause and resume code execution for concurrency

D. To replace all loops with asynchronous calls

Solution

1. Step 1: Understand Fiber's role

   Fibers allow pausing and resuming code blocks, enabling concurrency without threads.

2. Step 2: Compare options

   Only To pause and resume code execution for concurrency correctly describes Fibers' purpose; others describe unrelated features.

3. Final Answer:

   To pause and resume code execution for concurrency -> Option C

4. Quick Check:

   Fibers = pause and resume concurrency [OK]

Hint: Fibers let you pause and resume code easily [OK]

Common Mistakes:

• Thinking Fibers create real threads
• Assuming Fibers speed up database automatically
• Confusing Fibers with async loops

2. Which of the following is the correct way to start a Fiber in PHP?

easy

A. $fiber->run();

B. $fiber->execute();

C. $fiber->begin();

D. $fiber->start();

Solution

1. Step 1: Recall Fiber methods

   The Fiber class uses start() to begin execution.

2. Step 2: Check other options

   Methods like run(), begin(), and execute() do not exist for Fiber.

3. Final Answer:

   $fiber->start(); -> Option D

4. Quick Check:

   Fiber starts with start() method [OK]

Hint: Use start() to begin Fiber execution [OK]

Common Mistakes:

• Using run() instead of start()
• Trying to call execute() or begin()
• Confusing Fiber methods with thread methods

3. What will be the output of this PHP code using Fiber?

$fiber = new Fiber(function(): void {
    $value = Fiber::suspend('paused');
    echo "Resumed with: $value";
});

echo $fiber->start();
$fiber->resume('data');

medium

A. pausedResumed with: data

B. Resumed with: datapaused

C. paused

D. Resumed with: data

Solution

1. Step 1: Analyze Fiber start()

   The start() runs until Fiber::suspend('paused'), which returns 'paused'. So, echo outputs 'paused'.

2. Step 2: Analyze Fiber resume()

   The resume('data') continues after suspend, echoing "Resumed with: data".

3. Final Answer:

   pausedResumed with: data -> Option A

4. Quick Check:

   start() returns suspend value, resume() continues [OK]

Hint: start() returns suspend value, resume() continues execution [OK]

Common Mistakes:

• Assuming start() returns void
• Thinking resume() returns suspend value
• Mixing order of output strings

4. Identify the error in this Fiber code snippet:

$fiber = new Fiber(function() {
    echo "Start\n";
    Fiber::suspend();
    echo "End\n";
});

$fiber->resume();

medium

A. Fiber::suspend() cannot be called without a value

B. Fiber must be started with start(), not resume() first

C. Fiber constructor requires a return type declaration

D. Fiber cannot echo strings inside its function

Solution

1. Step 1: Check Fiber start method usage

   Fibers must be started with start() before calling resume().

2. Step 2: Validate other options

   Calling Fiber::suspend() without value is allowed; no return type needed; echo is valid inside Fiber.

3. Final Answer:

   Fiber must be started with start(), not resume() first -> Option B

4. Quick Check:

   start() first, then resume() [OK]

Hint: Always start Fiber with start() before resume() [OK]

Common Mistakes:

• Calling resume() before start()
• Thinking suspend() needs a value
• Expecting Fiber function to require return type

5. You want to run two Fibers concurrently to simulate two tasks. Which approach correctly switches between them to print alternating messages?

$fiber1 = new Fiber(function() {
    for ($i = 0; $i < 3; $i++) {
        echo "A$i ";
        Fiber::suspend();
    }
});

$fiber2 = new Fiber(function() {
    for ($i = 0; $i < 3; $i++) {
        echo "B$i ";
        Fiber::suspend();
    }
});

// Which code below correctly alternates execution?

A) {
    $fiber1->start();
    $fiber2->start();
    $fiber1->resume();
    $fiber2->resume();
}

B) {
    $fiber1->start();
    $fiber1->resume();
    $fiber2->start();
    $fiber2->resume();
}

C) {
    $fiber1->start();
    $fiber2->start();
    $fiber2->resume();
    $fiber1->resume();
}

D) {
    $fiber1->start();
    $fiber2->start();
    $fiber1->resume();
    $fiber1->resume();
}

hard

A. Start both fibers, then alternate resume calls: fiber1->resume(), fiber2->resume()

B. Start and resume fiber1 twice before starting fiber2

C. Start both fibers, then resume fiber2 before fiber1

D. Start both fibers, then resume fiber1 twice without resuming fiber2

Solution

1. Step 1: Understand Fiber suspension

   Each Fiber suspends after printing one message, so to alternate, we must resume them in turn.

2. Step 2: Analyze options for alternating resumes

   Start both fibers, then alternate resume calls: fiber1->resume(), fiber2->resume() starts both fibers, then resumes fiber1 and fiber2 alternately, producing alternating output. Others resume one fiber multiple times or in wrong order.

3. Final Answer:

   Start both fibers, then alternate resume calls: fiber1->resume(), fiber2->resume() -> Option A

4. Quick Check:

   Alternate resume calls for concurrency [OK]

Hint: Alternate resume calls to switch between fibers [OK]

Common Mistakes:

• Resuming one fiber multiple times before the other
• Starting fibers but not resuming correctly
• Resuming fibers in wrong order