public function getETag()
    {
        if (isset($this->cardData['etag'])) {
            return $this->cardData['etag'];
        } else {
            $data = $this->get();
            if (is_string($data)) {
                return '"'.md5($data).'"';
            } else {
                // We refuse to calculate the md5 if it's a stream.
                return null;
            }
        }
    }
public function getETag()
    {
        if (isset($this->cardData['etag'])) {
            return $this->cardData['etag'];
        } else {
            $data = $this->get();
            if (is_string($data)) {
                return '"'.md5($data).'"';
            } else {
                // We refuse to calculate the md5 if it's a stream.
                return null;
            }
        }
    }
public function getETag ( ) { if ( isset ( $ this -> cardData [ 'etag' ] ) ) { return $ this -> cardData [ 'etag' ] ; } else { $ data = $ this -> get ( ) ; if ( is_string ( $ data ) ) { return '"' . md5 ( $ data ) . '"' ; } else { // We refuse to calculate the md5 if it's a stream. return null ; } } }
Returns an ETag for this object.

@return string
Returns an ETag for this object .