src/HTTP/Request2.php
public function detach(SplObserver $observer)
    {
        foreach ($this->observers as $key => $attached) {
            if ($attached === $observer) {
                unset($this->observers[$key]);
                return;
            }
        }
    }
public function detach(SplObserver $observer)
    {
        foreach ($this->observers as $key => $attached) {
            if ($attached === $observer) {
                unset($this->observers[$key]);
                return;
            }
        }
    }
Detaches an existing observer

@param SplObserver $observer any object implementing SplObserver