Flushing output with PHP ob_flush on Nginx/PHP-FPM

Question

I'm trying to execute a PHP script which during execution provides the current status/percentage of completed actions. For do that I call the script with AJAX and I use the ob_flush for send the output to the client during script execution, it worked on Apache but now I'm porting the project on Nginx and I need compatibility for both. On Nginx I use PHP-FPM for handle PHP files, here's the test script which I'm trying to run correctly:

//SET CORRECT CONTENT-TYPE (THEY WILL BE JSON STRINGS SEPARED BY BREAKLINE)
header('Content-type: text/plain; charset=utf-8');
//DISABLE GZIP FOR THE SCRIPT
ini_set('zlib.output_compression', 'Off');
ini_set('output_buffering', 'Off');
ini_set('output_handler', '');

ob_end_clean();
set_time_limit(0);

for ( $i = 0 ; $i < 5 ; $i++ ){
    echo "{\"code\":" . $i . "}\n";
    //SEND OUTPUT TO CLIENT
    flush();
    ob_flush();
    sleep(1);
}

The problem is that when I run this I get the output just when the script ends the execution, so after about 5 seconds. Someone can tell me what I'm doing wrong?

For now I've resolved overloading the buffer by adding some extra spaces to the message using the function str_repeat(' ', 4096 * 8), it's a very inefficient and inelegant way to use flushing but it appears to be the only one with NGINX, anyway I have to give a look to the fastcgi_keep_conn on;" directive in the server configuration block in NGINX configuration file, maybe it can allows me to use normal PHP flush. — RyanJ
– RyanJ, Commented Aug 20, 2016 at 10:39

Yasuhiro Fujita · Accepted Answer · 2017-09-05 09:09:09Z

6

You should set HTTP response header 'X-Accel-Buffering' to 'no' when you don't want the Nginx to buffer the response from FastCGI server.

http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_buffering

answered Sep 5, 2017 at 9:09

Yasuhiro Fujita

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1 Comment

Breign Over a year ago

Calling header('X-Accel-Buffering: no'); in php script, or setting fastcgi_buffering: off; to turn off buffers globally.

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