When a promise is yielded, execution of the generator is interrupted until the promise is resolved. A success value is sent into the generator, while a failure reason is thrown into the generator. Using a coroutine, asynchronous code can be written without callbacks and be structured like synchronous code.
Inheritance: implements amp\Promise, use trait Amp\Internal\Placeholder
Coroutine Class Documentation
Exemple #1
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 /**
  * @param callable(callable(mixed $value): Promise $emit): \Generator $emitter
  *
  * @throws \Error Thrown if the callable does not return a Generator.
  */
 public function __construct(callable $emitter)
 {
     $result = $emitter($this->callableFromInstanceMethod("emit"));
     if (!$result instanceof \Generator) {
         throw new \Error("The callable did not return a Generator");
     }
     Loop::defer(function () use($result) {
         $coroutine = new Coroutine($result);
         $coroutine->when(function ($exception, $value) {
             if ($this->resolved) {
                 return;
             }
             if ($exception) {
                 $this->fail($exception);
                 return;
             }
             $this->resolve($value);
         });
     });
 }