src/HTTP/Request2.php
public function attach(SplObserver $observer)
    {
        foreach ($this->observers as $attached) {
            if ($attached === $observer) {
                return;
            }
        }
        $this->observers[] = $observer;
    }
public function attach(SplObserver $observer)
    {
        foreach ($this->observers as $attached) {
            if ($attached === $observer) {
                return;
            }
        }
        $this->observers[] = $observer;
    }
Attaches a new observer

@param SplObserver $observer any object implementing SplObserver