Things to note when using PHP flush function

ob_* series of functions operate the output buffer of PHP itself.

So, ob_flush refreshes PHP’s own buffer.

And flush, strictly speaking, can only be used in PHP as an apache Module (handler or filter) ) has an actual effect only when it is installed.
It is to refresh the buffer of the WebServer (which can be considered to refer specifically to apache).

Under the sapi of the apache module, flush will be called indirectly by calling the flush member function pointer of sapi_module. Apache's API: ap_rflush refreshes the output buffer of Apache. Of course, the manual also says that there are some other modules of Apache, which may change the result of this action..

Some Apache modules, such as mod_gzip, may output by themselves. Caching, which will cause the results produced by the flush() function to not be sent to the client browser immediately.

Even the browser will cache the received content before displaying it. For example, the Netscape browser caches content until it receives a newline or the beginning of an html tag, and does not display the entire table until it receives the tag.

Some versions of Microsoft Internet Explorer

will only start displaying the page after receiving 256 bytes, so some extra spaces must be sent to allow these browsers to display the page content.

So, the correct order to use the two is. First ob_flush, then flush,

Of course, under other sapi, you can not call flush, but in order to ensure the portability of your code, it is recommended to use them together.

<?php
// set_time_limit(0);
header(&#39;Content-Type: text/event-stream&#39;);
header(&#39;Cache-Control: no-cache&#39;);
// ob_end_flush();
// ini_set(&#39;output_buffering&#39;, 0);
// ini_set(&#39;implicit_flush&#39;, 1);
if (ob_get_level() == 0) ob_start();
echo str_repeat(&#39; &#39; ,4096);
$long = 60;
while($long > 0)
{
$time = date(&#39;r&#39;);
echo "data: The server time is: {$time}\n\n";
ob_flush();
flush();//break;
sleep(1);
$long --;
}
// var source=new EventSource("http://localhost:18000/sse.php");source.onmessage=function(event){console.info(event.data)};
?>

If you want to support nginx + fpm + php, you need to add a response header

header('X-Accel-Buffering: no');

This eliminates both proxy_buffering and (if you have nginx >= 1.5 .6), fastcgi_buffering. The fastcgi bit is crucial if you're using php-fpm. The header is also far more convenient to do on an as-needed basis.

Docs on X-Accel-Buffering http://nginx. org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_buffering ;

<?php
// set_time_limit(0);
header(&#39;Content-Type: text/event-stream&#39;);
header(&#39;Cache-Control: no-cache&#39;);
header(&#39;X-Accel-Buffering: no&#39;);
 
// ob_end_flush();
// ini_set(&#39;output_buffering&#39;, 0);
// ini_set(&#39;implicit_flush&#39;, 1);
 
// if (ob_get_level() == 0) ob_start();
// echo str_repeat(&#39; &#39; ,4096);
 
$long = 60;
while($long > 0)
{
    $time = date(&#39;r&#39;);
    echo "data: The server time is: {$time}\n\n";
    ob_flush();
     
    flush();//break;
    sleep(1);
    $long --;
}
// var source=new EventSource("http://localhost:18000/sse.php");source.onmessage=function(event){console.info(event.data)};
?>

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