Output buffering not working as expected?

Question

I have a long-running script and want to use output buffering to send output to the browser periodically.

I'm confused, because I've read a number of questions on here that said to use this:

while (...) {
    ob_start();
    // echo statements
    ob_end_flush();
}

But that didn't work for me. I also tried this:

while (...) {
    ob_start();
    // echo statements
    ob_flush();
    flush();
    ob_end_flush();
}

But that didn't work either. The only thing that seems to work is this:

while (...) {
    ob_end_clean();
    ob_start();
    // echo statements
    ob_flush();
    flush();
}

Why do I have to call ob_end_clean() first in order for output buffering to work?

Answer 1

Probably it depends on the rest of your code.

For me the following code works without a problem:

<?php
header( 'Content-type: text/html; charset=utf-8' );
$x = 1;

while ($x < 10) {
    echo $x."<br />";
    ob_flush();
    flush();
    sleep(1);
    ++$x;
}

You can use ob_implicit_flush() but it makes you don't need to run flash() each time you run ob_flush() so above code can be changed to:

<?php
header( 'Content-type: text/html; charset=utf-8' );
$x = 1;

ob_implicit_flush(true);

while ($x < 10) {
    echo $x."<br />";
    ob_flush();    
    sleep(1);
    ++$x;
}

You should also look at your header(). If in any of above codes I remove/comment line with header all the content will be displayed after scripts ends execution. Output buffering won't work as expected