A lightweight implementation of CommonJS Promises/A for PHP.
This file mostly code come from react/promise, thanks reactphp Team provide such a useful package.
Make sure that you have composer installed Composer.
If you don't have Composer run the below command
curl -sS https://getcomposer.org/installer | phpRun the installation
composer require skelan/simple-promiseA Deferred represents a computation or unit of work that may not have completed yet. Typically (but not always), that computation will be something that executes asynchronously and completes at some point in the future.
While a deferred represents the computation itself, a Promise represents the result of that computation. Thus, each deferred has a promise that acts as a placeholder for its actual result.
A deferred represents an operation whose resolution is pending. It has separate promise and resolver parts.
$deferred = new Skelan\SimplePromise\Deferred();
$promise = $deferred->promise();
$deferred->resolve(mixed $value = null);
$deferred->reject(mixed $reason = null);A few simple examples to show how the mechanics of Promises/A forwarding works. These examples are contrived, of course, and in real usage, promise chains will typically be spread across several function calls, or even several levels of your application architecture.
Resolved promises forward resolution values to the next promise.
The first promise, $deferred->promise(), will resolve with the value passed
to $deferred->resolve() below.
Each call to then() returns a new promise that will resolve with the return
value of the previous handler. This creates a promise "pipeline".
$deferred = new Skelan\SimplePromise\Deferred();
$deferred->promise()
->then(function ($x) {
// $x will be the value passed to $deferred->resolve() below
// and returns a *new promise* for $x + 1
return $x + 1;
})
->then(function ($x) {
// $x === 2
// This handler receives the return value of the
// previous handler.
return $x + 1;
})
->then(function ($x) {
// $x === 3
// This handler receives the return value of the
// previous handler.
return $x + 1;
})
->then(function ($x) {
// $x === 4
// This handler receives the return value of the
// previous handler.
echo 'Resolve ' . $x;
});
$deferred->resolve(1); // Prints "Resolve 4"Rejected promises behave similarly, and also work similarly to try/catch: When you catch an exception, you must rethrow for it to propagate.
Similarly, when you handle a rejected promise, to propagate the rejection, "rethrow" it by either returning a rejected promise, or actually throwing (since promise translates thrown exceptions into rejections)
$deferred = new Skelan\SimplePromise\Deferred();
$deferred->promise()
->then(function ($x) {
throw new \Exception($x + 1);
})
->otherwise(function (\Exception $x) {
// Propagate the rejection
throw $x;
})
->otherwise(function ($x) {
echo 'Reject ' . $x->getMessage(); // 3
});
$deferred->resolve(1); // Prints "Reject 3"Just like try/catch, you can choose to propagate or not. Mixing resolutions and rejections will still forward handler results in a predictable way.
try {
return doSomething();
} catch(\Exception $e) {
return handleError($e);
} finally {
doFinally();
}$deferred = new Skelan\SimplePromise\Deferred();
$deferred->promise()
->then(function ($x) {
return $x + 1;
})
->then(function ($x) {
throw new \Exception($x + 1);
})
->otherwise(function (\Exception $x) {
//catch exception
var_dump('otherwise: ' . ($x->getMessage() + 1)); //4
})
->always(function () {
//finally
var_dump('finally ');
});
$deferred->resolve(1); swoole is awesome extension of php
function remoteRequest() {
$deferred = new \Skelan\SimplePromise\Deferred(function (\Skelan\SimplePromise\PromiseInterface $promise) {
var_dump('call cancel.');
});
\Swoole\Timer::after(1000, function() use($deferred) {
$deferred->resolve('finish: ' . time());
});
return $deferred->promise();
}
remoteRequest()->then(function ($value) {
var_dump('resolve: ' . time());
var_dump($value);
throw new \Exception('xxx');
}, function($reason) {
var_dump($reason);
})->otherwise(function(\Throwable $exception) {
var_dump('exception: ' . $exception->getMessage());
})->always(function($value) {
var_dump('otherwise: ' . $value);
});Released under the MIT license.