src/Observable.php
public function distinctUntilKeyChanged(callable $keySelector = null, callable $comparer = null): Observable
    {
        return $this->lift(function () use ($keySelector, $comparer) {
            return new DistinctUntilChangedOperator($keySelector, $comparer);
        });
    }
public function distinctUntilKeyChanged(callable $keySelector = null, callable $comparer = null): Observable
    {
        return $this->lift(function () use ($keySelector, $comparer) {
            return new DistinctUntilChangedOperator($keySelector, $comparer);
        });
    }
public function distinctUntilKeyChanged ( callable $ keySelector = null , callable $ comparer = null ) : Observable { return $ this -> lift ( function ( ) use ( $ keySelector , $ comparer ) { return new DistinctUntilChangedOperator ( $ keySelector , $ comparer ) ; } ) ; }
Variant of distinctUntilChanged that takes a key selector
and the comparer.

@param callable $keySelector
@param callable $comparer
@return Observable

@demo distinct/distinctUntilKeyChanged.php
@operator
@reactivex distinct
Variant of distinctUntilChanged that takes a key selector and the comparer .