PHP Error: ob_flush() [ref.outcontrol]: failed to flush buffer. No buffer to flush

Question

Could someone please save these 2 files and run them and tell me why I get the error \" ob_flush() [ref.outcontrol]: failed to flush buffer. No buffer to flush\". I tried go

Answer 1

You only need ob_flush() if an output buffer is active (for example by ob_start(), or by configuration settings). If you haven't, just remove the ob_flush(). Or you can make it conditional:

 if( ob_get_level() > 0 ) ob_flush();

Answer 2

Where is ob_start()?

ob_flush flushes the output buffer to your file handle. Maybe you have it wrong.

An example:

ob_start(); //start output buffering
echo 'hello world'; //not outputed
ob_flush(); //sends the output buffer so displays hello world.

manual

Answer 3

I think you are confusing ob_flush() with flush(). While ob_start() and ob_flush() handles a PHP internal output buffer that catches all outputs, flush() is the normal function that flushes STDOUT like in other programming languages.

Example:

<?php
ob_start();
echo "Foobar\nFoobar\nFoobar\n";
// Nothing printed yet
ob_flush(); // Now it is printed.

echo "Foobar\n"; // Printed directly, because contains a line ending.

echo "Foobar"; // Not printed, because normally buffers are flushed on line endings
flush();  // Printed.

EDIT:

Your output is not printed, because your webserver may buffer the contents. Try to turn off compression and output buffering:

@apache_setenv('no-gzip', 1);
@ini_set('zlib.output_compression', 0);
@ini_set('implicit_flush', 1);

Please also keep in mind, that Safari and Internet Explorer have an internal 1K buffer. So you need to add 1 KB of padding data (like spaces), to make them render.

EDIT 2: Your implementation is broken. You want to poll your data with ajax. Use jQuery on the client side:

<div id="counter">0%</div>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js">
<script type="text/javascript">
function doPoll(){
    $.post('script-that-returns-stuff.php', function(data) {
        $("#counter").html(data);
        setTimeout(doPoll,5000);
    });
}
doPoll();
</script>

Then in script-that-returns-stuff.php:

<?php
$file = explode("\n", file_get_contents("/tmp/output.txt"));
$last_line = $file[count($file)-1];
echo $last_line."%";