PHP GZip and Server Sent Event Streams

Question

I'm writing a server sent event stream in PHP and I receive the error:

"failed to flush buffer zlib output compression"

This I believe is due to trying to flush the gzipped output.

Here's my PHP code:

header ("Content-Type: text/event-stream\n\n");
header ("Cache-Control: no-cache");

echo "data: {$json}";
echo "\n\n";

ob_flush(); // ERROR HERE
flush();

My question is what is the best way to get this working - ideally without disabling gzip in apache - can it be turned off in PHP?

I tried this but it didn't work:

if(ini_get('zlib.output_compression')){
    ini_set('zlib.output_compression', 'Off');
}

Answer 1

You cannot use zlib output compression along ob_ output handler. See the php docs on zlib.output_compression, it states it multiple times.

If found out that the easiest way to enable output compression in php is to just do this:

ini_set("zlib.output_compression", 1);
ini_set("zlib.output_compression_level", 9);

And loose all the ob_* stuff. Now when a client requests a page with a header like :

Accept-Encoding: gzip, deflate

zlib will gzip your response body for you AND it will set this for you in the response:

Content-Encoding: gzip

I spent hours of my life on this before realising how simple it is with those 2 lines. and don't use any flush at all implicitely