name : ContentLength.rst Adding Content-Length header ============= Adding a ``Content-Length`` header for ``ZipStream`` can be achieved by using the options ``SIMULATION_STRICT`` or ``SIMULATION_LAX`` in the ``operationMode`` parameter. In the ``SIMULATION_STRICT`` mode, ``ZipStream`` will not allow to calculate the size based on reading the whole file. ``SIMULATION_LAX`` will read the whole file if neccessary. ``SIMULATION_STRICT`` is therefore useful to make sure that the size can be calculated efficiently. .. code-block:: php use ZipStream\OperationMode; use ZipStream\ZipStream; $zip = new ZipStream( operationMode: OperationMode::SIMULATE_STRICT, // or SIMULATE_LAX defaultEnableZeroHeader: false, sendHttpHeaders: true, outputStream: $stream, ); // Normally add files $zip->addFile('sample.txt', 'Sample String Data'); // Use addFileFromCallback and exactSize if you want to defer opening of // the file resource $zip->addFileFromCallback( 'sample.txt', exactSize: 18, callback: function () { return fopen('...'); } ); // Read resulting file size $size = $zip->finish(); // Tell it to the browser header('Content-Length: '. $size); // Execute the Simulation and stream the actual zip to the client $zip->executeSimulation();