public function exclusivelySingle()
    {
        if (count($this) === 0) {
            return false;
        }

        foreach (array_keys($this->getDataPlaceHolder()) as $key) {
            $v = $this[$key];
            if (is_null($v) || $v instanceof Container) {
                return false;
            }
        }

        return true;
    }
public function exclusivelySingle()
    {
        if (count($this) === 0) {
            return false;
        }

        foreach (array_keys($this->getDataPlaceHolder()) as $key) {
            $v = $this[$key];
            if (is_null($v) || $v instanceof Container) {
                return false;
            }
        }

        return true;
    }
public function exclusivelySingle ( ) { if ( count ( $ this ) === 0 ) { return false ; } foreach ( array_keys ( $ this -> getDataPlaceHolder ( ) ) as $ key ) { $ v = $ this [ $ key ] ; if ( is_null ( $ v ) || $ v instanceof Container ) { return false ; } } return true ; }
Wether the collection contains exclusively single cardinality values. If the container
is empty or contains a null value, false is returned.

@return boolean
Wether the collection contains exclusively single cardinality values . If the container is empty or contains a null value false is returned .