public function addReferrer($referrer)
    {
        if (null === $this->referrers) {
            $this->referrers = new ArrayCollection();
        }

        $this->referrers->add($referrer);

        return $this;
    }
public function addReferrer($referrer)
    {
        if (null === $this->referrers) {
            $this->referrers = new ArrayCollection();
        }

        $this->referrers->add($referrer);

        return $this;
    }
public function addReferrer ( $ referrer ) { if ( null === $ this -> referrers ) { $ this -> referrers = new ArrayCollection ( ) ; } $ this -> referrers -> add ( $ referrer ) ; return $ this ; }
Add a referrer to this document.

@param $referrer

@return $this;
Add a referrer to this document .