public function add($keys)
    {
        foreach ($this->expandKeys((array) $keys) as $key) {
            if (!$this->has($key)) {
                $this->keys[] = $key;
            }
        }

        return $this;
    }
public function add($keys)
    {
        foreach ($this->expandKeys((array) $keys) as $key) {
            if (!$this->has($key)) {
                $this->keys[] = $key;
            }
        }

        return $this;
    }
public function add ( $ keys ) { foreach ( $ this -> expandKeys ( ( array ) $ keys ) as $ key ) { if ( ! $ this -> has ( $ key ) ) { $ this -> keys [ ] = $ key ; } } return $ this ; }
Add one or more keys.
Duplicate keys will be silently ignored.

@param string|array|mixed $keys

@return $this
Add one or more keys . Duplicate keys will be silently ignored .