# Deferred
Similar to a Deferred of Kotlin carries a function like **`await()`** to return a result when the waiting task is completed.
Keep in mind that when using the Deferred class, you need to specify that it is a [**`Generator`**](https://www.php.net/manual/en/language.generators.php) callback.
```php
CoroutineGen::runNonBlocking(
function() : Generator {
$deferred = new Deferred(function() : Generator {
return yield file_get_contents('http://www.weather.com.cn/data/cityinfo/101270101.html');
});
$data = yield from $deferred->await();
var_dump($data);
},
function() : Generator {
yield var_dump("END!");
},
function() {
var_dump("START!");
},
function() {
var_dump("Hello World");
}
);
```
Output:
```
string(6) "START!"
string(11) "Hello World"
string(4) "END!"
string(10989) "
...."
```
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