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PHP True Async vs Python asyncio: API Comparison

This document compares the coroutine APIs of PHP True Async and Python's asyncio module.

Overview

Aspect PHP True Async Python asyncio
Model Implicit async (no keywords in function signatures) Explicit async (async def keyword required)
Coroutine Creation spawn(callable, ...args) asyncio.create_task(coro)
Awaiting await($completable) await expression
Yield Control suspend() await asyncio.sleep(0)
Cancellation Built-in, cooperative Built-in, cooperative

Coroutine Definition

Feature PHP True Async Python asyncio
Syntax Regular function (no special syntax) async def function_name():
Marking None required async keyword mandatory
Return Type Any (transparent) Coroutine object
Callable in sync context Yes (runs synchronously) No (returns coroutine object)

Code Examples

PHP True Async:

// Any function can be a coroutine - no special syntax
function fetchData(string $url): string {
    return file_get_contents($url);
}

// Launch as coroutine
$coro = spawn(fetchData(...), 'https://example.com');

Python asyncio:

# Must be marked with async
async def fetch_data(url: str) -> str:
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.text()

# Create task
task = asyncio.create_task(fetch_data('https://example.com'))

Coroutine Launching

Feature PHP True Async Python asyncio
Function spawn(callable, ...args) asyncio.create_task(coro)
Returns Coroutine object Task object
Arguments Passed directly to spawn Passed when calling async function
Start behavior Queued, starts on scheduler iteration Starts on next event loop iteration

Code Examples

PHP True Async:

use function Async\spawn;

// Arguments passed to spawn()
$coro = spawn('file_get_contents', 'https://php.net');

// Using first-class callable
$coro = spawn(fetchData(...), 'https://php.net');

Python asyncio:

import asyncio

# Arguments passed to coroutine function
task = asyncio.create_task(fetch_data('https://python.org'))

# Alternative: asyncio.ensure_future()
task = asyncio.ensure_future(fetch_data('https://python.org'))

Awaiting Results

Feature PHP True Async Python asyncio
Syntax await($completable) await expression
Type Function call Language keyword
Multiple awaits Same result (idempotent) Same result (idempotent)
With timeout await($coro, $cancellation) asyncio.wait_for(coro, timeout)

Code Examples

PHP True Async:

use function Async\spawn;
use function Async\await;

$coro = spawn(fetchData(...), 'https://php.net');
$result = await($coro);

// With cancellation/timeout
$result = await(
    spawn(fetchData(...), 'https://php.net'),
    spawn('sleep', 5)  // timeout after 5 seconds
);

Python asyncio:

import asyncio

task = asyncio.create_task(fetch_data('https://python.org'))
result = await task

# With timeout
result = await asyncio.wait_for(
    fetch_data('https://python.org'),
    timeout=5.0
)

Yielding Control (Suspension)

Feature PHP True Async Python asyncio
Function suspend() await asyncio.sleep(0)
Explicit yield Yes, dedicated function No, use sleep(0) hack
Throws on cancel Cancellation exception CancelledError exception

Code Examples

PHP True Async:

use function Async\suspend;

function processItems(array $items): void {
    foreach ($items as $item) {
        process($item);
        suspend(); // Yield control to other coroutines
    }
}

Python asyncio:

import asyncio

async def process_items(items: list) -> None:
    for item in items:
        process(item)
        await asyncio.sleep(0)  # Yield control

Cancellation

Feature PHP True Async Python asyncio
Method $coroutine->cancel(?Cancellation) task.cancel(msg=None)
Exception \Cancellation (extends \Throwable) asyncio.CancelledError (extends BaseException)
Suppression Auto-suppressed if unhandled in coroutine Must be caught or propagates
Multiple cancels First wins Last wins
Self-cancellation Allowed (delayed effect) Allowed (immediate)

Exception Hierarchy

PHP True Async:

\Throwable
├── \Error
├── \Exception
└── \Cancellation          ← Separate from Exception tree
    └── \Async\AsyncCancellation

Python asyncio:

BaseException
├── Exception
└── CancelledError         ← Separate from Exception tree (since Python 3.8)

Code Examples

PHP True Async:

use function Async\spawn;
use function Async\await;

$coro = spawn(function() {
    try {
        await(spawn('sleep', 10));
    } catch (\Cancellation $e) {
        // Cleanup logic
        echo "Cancelled: " . $e->getMessage();
    }
});

$coro->cancel(new \Cancellation("Timeout"));

Python asyncio:

import asyncio

async def my_task():
    try:
        await asyncio.sleep(10)
    except asyncio.CancelledError:
        print("Task was cancelled")
        raise  # Re-raise is recommended

task = asyncio.create_task(my_task())
task.cancel()

Coroutine State Inspection

Method/Property PHP True Async Python asyncio
Get ID $coro->getId() N/A (use id(task))
Is running $coro->isRunning() N/A
Is completed $coro->isCompleted() task.done()
Is cancelled $coro->isCancelled() task.cancelled()
Get result $coro->getResult() task.result()
Get exception $coro->getException() task.exception()
Is started $coro->isStarted() N/A (always started)
Is suspended $coro->isSuspended() N/A

Cleanup (Finally)

Feature PHP True Async Python asyncio
Method $coro->finally(callback) task.add_done_callback(cb)
Function Async\finally(callback) N/A
Callback args Receives coroutine Receives task
Execution Concurrent (in separate coroutine) Sequential

Code Examples

PHP True Async:

use function Async\spawn;
use function Async\finally;

function task(): void {
    $file = fopen('file.txt', 'r');
    finally(fn() => fclose($file));

    // Work with file...
}

spawn('task');

Python asyncio:

import asyncio

async def task():
    file = open('file.txt', 'r')
    try:
        # Work with file...
        pass
    finally:
        file.close()

# Or with callback
def cleanup(task):
    print(f"Task {task} completed")

t = asyncio.create_task(task())
t.add_done_callback(cleanup)

Multiple Coroutines

Operation PHP True Async Python asyncio
Wait all Via Scope RFC asyncio.gather(*coros)
Wait first Via Scope RFC asyncio.wait(tasks, return_when=FIRST_COMPLETED)
Wait any Via Scope RFC asyncio.wait(tasks, return_when=FIRST_COMPLETED)
Get all coroutines Via Scope RFC asyncio.all_tasks()

Code Examples

PHP True Async:

use function Async\spawn;
use function Async\await;
use function Async\get_coroutines;

$coro1 = spawn(fetchData(...), 'url1');
$coro2 = spawn(fetchData(...), 'url2');

$result1 = await($coro1);
$result2 = await($coro2);

// Get all coroutines
$all = get_coroutines();

Python asyncio:

import asyncio

task1 = asyncio.create_task(fetch_data('url1'))
task2 = asyncio.create_task(fetch_data('url2'))

# Wait for all
results = await asyncio.gather(task1, task2)

# Get all tasks
all_tasks = asyncio.all_tasks()

Graceful Shutdown

Feature PHP True Async Python asyncio
Trigger Unhandled exception / Async\shutdown() loop.stop() / signal handlers
Behavior Cancels all coroutines, then continues Stops loop immediately
Exit/Die Triggers graceful shutdown sys.exit() raises SystemExit
Deadlock detection Built-in, throws DeadlockError No built-in detection

Key Philosophical Differences

Aspect PHP True Async Python asyncio
Function coloring No (any function can be coroutine) Yes (async functions are different)
Cancellation default Cancellable by design Cancellable by design
Code migration Minimal changes needed Requires async/await everywhere
I/O transparency Same API for sync/async Different APIs (aiohttp vs requests)
Entry point Any code can use async Requires asyncio.run() or event loop