lib/HTTP/ConditionalGet.php
protected function _isCacheValid()
    {
        if (null === $this->_etag) {
            // lmTime is copied to ETag, so this condition implies that the
            // server sent neither ETag nor Last-Modified, so the client can't
            // possibly has a valid cache.
            return false;
        }
        $isValid = ($this->resourceMatchedEtag() || $this->resourceNotModified());
        if ($isValid) {
            $this->_headers['_responseCode'] = 'HTTP/1.0 304 Not Modified';
        }

        return $isValid;
    }
protected function _isCacheValid()
    {
        if (null === $this->_etag) {
            // lmTime is copied to ETag, so this condition implies that the
            // server sent neither ETag nor Last-Modified, so the client can't
            // possibly has a valid cache.
            return false;
        }
        $isValid = ($this->resourceMatchedEtag() || $this->resourceNotModified());
        if ($isValid) {
            $this->_headers['_responseCode'] = 'HTTP/1.0 304 Not Modified';
        }

        return $isValid;
    }
protected function _isCacheValid ( ) { if ( null === $ this -> _etag ) { // lmTime is copied to ETag, so this condition implies that the // server sent neither ETag nor Last-Modified, so the client can't // possibly has a valid cache. return false ; } $ isValid = ( $ this -> resourceMatchedEtag ( ) || $ this -> resourceNotModified ( ) ) ; if ( $ isValid ) { $ this -> _headers [ '_responseCode' ] = 'HTTP/1.0 304 Not Modified' ; } return $ isValid ; }
Determine validity of client cache and queue 304 header if valid

@return bool
Determine validity of client cache and queue 304 header if valid