src/Observable.php
public static function interval(int $interval, AsyncSchedulerInterface $scheduler = null): IntervalObservable
    {
        return new IntervalObservable($interval, $scheduler ?: Scheduler::getAsync());
    }
public static function interval(int $interval, AsyncSchedulerInterface $scheduler = null): IntervalObservable
    {
        return new IntervalObservable($interval, $scheduler ?: Scheduler::getAsync());
    }
public static function interval ( int $ interval , AsyncSchedulerInterface $ scheduler = null ) : IntervalObservable { return new IntervalObservable ( $ interval , $ scheduler ? : Scheduler :: getAsync ( ) ) ; }
Returns an Observable that emits an infinite sequence of ascending integers starting at 0, with a constant interval of time of your choosing between emissions.

@param $interval int Period for producing the values in the resulting sequence (specified as an integer denoting milliseconds).
@param null|AsyncSchedulerInterface|SchedulerInterface $scheduler
@return IntervalObservable An observable sequence that produces a value after each period.

@demo interval/interval.php
@operator
@reactivex interval
Returns an Observable that emits an infinite sequence of ascending integers starting at 0 with a constant interval of time of your choosing between emissions .