PHP Progress Bar

An interesting idea was posted to eVolt’s TheList in the form of a tip: using PHP’s flushing buffer to create a progress bar for large PHP applications. Juha Suni, the author of the tip, provided the following code, noting, that “you can use the flush()-function to push more data to the browser while the script is running. This data being elements for small pieces of the progress bar, you can rather easily have a universal solution for all heavy scripts”. The code below is as posted, the only changes are a couple of formatting tweaks for display on this site. I haven’t implemented it as of yet, so I can’t vouch for it’s functionality.

ob_end_flush(); // This should be called at start

// Load all data and process it ready for looping

// Do some preliminary calculations, such as:
$totalloops = 38;
$percent_per_loop = 100 / $totalloops;
$prev_percent = 0;

// print html/css for the part above the progress bar
// as well as possible background of the actual progress bar
// in such a way that the images for the progress bar (coming next)
// align themselves nicely
// (This example fits 100 images next to each other, each
// representing 1 percent of progress.

// Start looping:
for($i=1;$i< =$totalloops;$i++) {

    // do stuff
    // echo progress if at least an advance of 1 percent
    // occured since last loop
    $percent_now = round($i * $percent_per_loop);
    if($percent_now != $percent_last) {
        $difference = $percent_now - $percent_last;
        for($j=1;$j<=$difference;$j++) {
            echo '';
            }
       $percent_last = $percent_now;
       flush(); // Push the new data to the browser;
        }
}

// In the end print necessary code to the end of the html.

Juha notes, “on some occasions, the webserver, proxy or the client browser can buffer data no matter what you do, so this will not work 100% for everyone at every situation”. Still, this is a great idea, and one sorely needed for some major PHP apps.

Update: Juha has posted a nice demo of the script, which “loops the sleep(1)-command for 14 times”. He also added a counter that displays the percentage that has been completed. Juha mentioned that he hopes to find the time to clean it up and implement the counter as a package for use in other scripts and projects. That would be great to see!

Update 2: Juha has posted a zipped up collection of the PHP source files and associated images.