Question

I have some serious (or better say: strange) issues with the HTTP-header: Content-Encoding.

I want to gzip my content before sending it to the clients browser. For this I am checking if the clients browser accepts gzip and if so I am using ob_start("ob_gzhandler") and setting the content-encoding: $response->addHeader("Content-Encoding", "gzip");

• I think my problem is the manual setting of the Content-Encoding header.
  If I use $response->addHeader("Content-Encoding", "gzip"); the content is only shown in Opera.

• If I use $response->addHeader("Content-Encoding", "'gzip'"); the content is shown correct in all browsers, but gzip compression checks say that it is not compressed and the W3C HTML Validation service cannot encode the page:

The error was: Don’t know how to decode Content-Encoding ”gzip”

• If I don’t use the line and online use ob_start("ob_gzhandler") the page can only be shown in opera

My complete lines of code, which does correct output in browser is following:

$accEncoding = $request->getHeader("http_accept_encoding");
if($accEncoding !== NULL && substr_count($accEncoding, 'gzip')) {
    ob_start("ob_gzhandler");
    $response->addHeader("Content-Encoding", "'gzip'");
    $response->addHeader("Vary", "Accept-Encoding");
} else {
    ob_start();
}

Am I using the ob_gzhandler wrong or am I doing any other mistake here? I am very confused about the correct handling of gzip output.

Answer 1

ob_gzhandler already verifies that the browser supports gzip compression:

Before ob_gzhandler() actually sends compressed data, it determines what type of content encoding the browser will accept (“gzip”, “deflate” or none at all) and will return its output accordingly.

It also sets the Content-Encoding header accordingly.

Also note that using zlib.output_compression is preferred over ob_gzhandler().