# Some common methods

Chaining Promises

```php
function testPromise1() : Promise {
    return new Promise(function ($resolve, $reject) {
        System::setTimeout(function () use ($resolve) {
            $resolve("A");
        }, 1000);
    });
}

function testPromise2() : Promise {
    return new Promise(function ($resolve, $reject) {
        System::setTimeout(function () use ($resolve) {
            $resolve("B");
        }, 1000);
    });
}

function testPromise3() : Promise {
    return new Promise(function ($resolve, $reject) {
        System::setTimeout(function () use ($resolve) {
            $resolve("C");
        }, 1000);
    });
}

function testPromise4() : Promise {
    return new Promise(function ($resolve, $reject) {
        System::setTimeout(function () use ($resolve) {
            $resolve("D");
        }, 1000);
    });
}

testPromise1()->then(function ($value) {
    var_dump($value);
    return testPromise2();
})->then(function ($value) {
    var_dump($value);
    return testPromise3();
})->then(function ($value) {
    var_dump($value);
    return testPromise4();
})->then(function ($value) {
    var_dump($value);
})->catch(function ($value) {
    var_dump($value);
})->finally(function() {
    var_dump("Complete!");
});
```

Promise Arrow

```php
Promise::c(fn($resolve) => $resolve("OK"))->then(fn($result) => var_dump($result));
```

Advanced Mix Async Await + Promise

```php
function request($type) {
    return new Promise(function ($resolve, $reject) use ($type) {
        System::setTimeout(function () use ($resolve, $reject, $type) {
            $type === 'success' ? $resolve('success') : $reject('error');
        }, 1000);
    });
}

function getData() {
    new Async(function () {
        [$data, $error] = Async::await(handleRequest(request('success')));
        if ($error) {
            echo $error;
        } else {
            echo $data;
        }
    });
}

function handleRequest(Promise $promise) {
    return $promise->then(fn($data) => [$data, null])->catch(fn($error) => [null, $error]);
}

getData();
```


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