ent-Type'] ) ) {
				$content_type = $response_headers['kv']['Content-Type'];
			}
		}

		$time = time();
		$cache = $this->_get_cache( $this->_page_key_extension['group'] );

		/**
		 * Store different versions of cache
		 */
		$buffers = array();
		$something_was_set = false;

		foreach ( $compressions_to_store as $_compression ) {
			$this->_set_extract_page_key(
				array_merge( $this->_page_key_extension,
					array(
						'compression' => $_compression,
						'content_type' => $content_type ) ), true );
			if ( empty( $this->_page_key ) )
				continue;

			// Compress content
			$buffers[$_compression] = $this->_compress( $buffer, $_compression );

			// Store cache data
			$_data = array(
				'404' => $is_404,
				'headers' => $headers,
				'time' => $time,
				'content' => $buffers[$_compression]
			);
			if ( !empty( $_compression ) ) {
				$_data['c'] = $_compression;
			}
			if ( $has_dynamic )
				$_data['has_dynamic'] = true;

			$_data = apply_filters( 'w3tc_pagecache_set', $_data, $this->_page_key,
				$this->_page_group );

			if ( !empty( $_data ) ) {
				$cache->set( $this->_page_key, $_data, $this->_lifetime, $this->_page_group );
				$something_was_set = true;
			}
		}

		if ( $something_was_set ) {
			$this->process_status = 'miss_fill';
		} else {
			$this->process_status = 'miss_third_party';
		}

		// Change buffer if using compression
		if ( defined( 'W3TC_PAGECACHE_OUTPUT_COMPRESSION_OFF' ) ) {
			$compression_header = false;
		} elseif ( $compression_of_returned_content &&
			isset( $buffers[$compression_of_returned_content] ) ) {
			$buffer = $buffers[$compression_of_returned_content];
		}

		// Calculate content etag
		$etag = md5( $buffer );

		// Send headers
		$this->_send_headers( $is_404, $time, $etag, $compression_header,
			$headers );
		return $buffer;
	}

	public function w3tc_usage_statistics_of_request( $storage ) {
		global $w3tc_start_microtime;
		$time_ms = 0;
		if ( !empty( $w3tc_start_microtime ) ) {
			$time_ms = (int)( ( microtime( true ) - $w3tc_start_microtime ) * 1000 );
			$storage->counter_add( 'pagecache_requests_time_10ms', (int)( $time_ms / 10 ) );
		}

		if ( !empty( $this->process_status ) ) {
			// see registered keys in PgCache_Plugin.w3tc_usage_statistics_metrics
			$storage->counter_add( 'php_requests_pagecache_' . $this->process_status, 1 );

			if ( $this->_debug ) {
				self::log( 'finished in ' . $time_ms .
					' size ' . $this->output_size .
					' with process status ' .
					$this->process_status .
					' reason ' . $this->cache_reject_reason);
			}
		}
	}

	/**
	 * Log.
	 */
	static protected function log( $msg ) {
		$data = sprintf(
			"[%s] [%s] [%s] %s\n", date( 'r' ),
			isset( $_SERVER['REQUEST_URI'] ) ? filter_var( stripslashes( $_SERVER['REQUEST_URI'] ), FILTER_SANITIZE_URL ) : '',
			! empty( $_SERVER['HTTP_REFERER'] ) ? htmlspecialchars( $_SERVER['HTTP_REFERER'] ) : '-',
			$msg
		);
		$data = strtr( $data, '<>', '..' );

		$filename = Util_Debug::log_filename( 'pagecache' );

		return @file_put_contents( $filename, $data, FILE_APPEND );
	}
}