src/Observable.php
public function distinctUntilChanged(callable $comparer = null): Observable
    {
        return $this->lift(function () use ($comparer) {
            return new DistinctUntilChangedOperator(null, $comparer);
        });
    }
public function distinctUntilChanged(callable $comparer = null): Observable
    {
        return $this->lift(function () use ($comparer) {
            return new DistinctUntilChangedOperator(null, $comparer);
        });
    }
public function distinctUntilChanged ( callable $ comparer = null ) : Observable { return $ this -> lift ( function ( ) use ( $ comparer ) { return new DistinctUntilChangedOperator ( null , $ comparer ) ; } ) ; }
A variant of distinct that only compares emitted items from the source Observable against their immediate predecessors in order to determine whether or not they are distinct.

@param callable $comparer
@return Observable

@demo distinct/distinctUntilChanged.php
@operator
@reactivex distinct
A variant of distinct that only compares emitted items from the source Observable against their immediate predecessors in order to determine whether or not they are distinct .