Upload Progress Bar in PHP

If you have APC installed, it has a callback hook for upload progress.

Rasmus Lerdorf (PHP's creator) has a sample of this using YUI (oh, and here's the PHP source).

See the documentation here.

I'm sorry to say that to the best of my knowledge a pure PHP upload progress bar, or even a PHP/Javascript upload progress bar is not possible because of how PHP works. Your best bet is to use some form of Flash uploader.

AFAIK This is because your script is not executed until all the superglobals are populated, which includes $_FILES. By the time your PHP script gets called, the file is fully uploaded.

EDIT: This is no longer true. It was in 2010.

Implementation of the upload progress bar is easy and doesn't require any additional PHP extension, JavaScript or Flash. But you need PHP 5.4 and newer.

You have to enable collecting of the upload progress information by setting the directive session.upload_progress.enabled to On in php.ini.

Then add a hidden input to the HTML upload form just before any other file inputs. HTML attribute name of that hidden input should be the same as the value of the directive session.upload_progress.name from php.ini (eventually preceded by session.upload_progress.prefix). The value attribute is up to you, it will be used as part of the session key.

HTML form could looks like this:

<form action="upload.php" method="POST" enctype="multipart/form-data">
   <input type="hidden" name="<?php echo ini_get('session.upload_progress.prefix').ini_get('session.upload_progress.name'); ?>" value="myupload" />
   <input type="file" name="file1" />
   <input type="submit" />
</form>

When you send this form, PHP should create a new key in the $_SESSION superglobal structure which will be populated with the upload status information. The key is concatenated name and value of the hidden input.

In PHP you can take a look at populated upload information:

var_dump($_SESSION[
    ini_get('session.upload_progress.prefix')
   .ini_get('session.upload_progress.name')
   .'_myupload'
]);

The output will look similarly to the following:

$_SESSION["upload_progress_myupload"] = array(
  "start_time" => 1234567890,   // The request time
  "content_length" => 57343257, // POST content length
  "bytes_processed" => 54321,   // Amount of bytes received and processed
  "done" => false,              // true when the POST handler has finished, successfully or not
  "files" => array(
    0 => array(
      "field_name" => "file1",    // Name of the <input /> field
      // The following 3 elements equals those in $_FILES
      "name" => "filename.ext",
      "tmp_name" => "/tmp/phpxxxxxx",
      "error" => 0,
      "done" => false,            // True when the POST handler has finished handling this file
      "start_time" => 1234567890, // When this file has started to be processed
      "bytes_processed" => 54321, // Number of bytes received and processed for this file
    )
  )
);

There is all the information needed to create a progress bar — you have the information if the upload is still in progress, the information how many bytes is going to be transferred in total and how many bytes has been transferred already.

To present the upload progress to the user, write an another PHP script than the uploading one, which will only look at the upload information in the session and return it in the JSON format, for example. This script can be called periodically, for example every second, using AJAX and information presented to the user.

You are even able to cancel the upload by setting the $_SESSION[$key]['cancel_upload'] to true.

For detailed information, additional settings and user's comments see PHP manual.

Gears and HTML5 have a progress event in the HttpRequest object for submitting a file upload via AJAX.

http://developer.mozilla.org/en/Using_files_from_web_applications

Your other options as already answered by others are:

1. Flash based uploader.
2. Java based uploader.
3. A second comet-style request to the web server or a script to report the size of data received. Some webservers like Lighttpd provide modules to do this in-process to save the overhead of calling an external script or process.

Technically there is a forth option, similar to YouTube upload, with Gears or HTML5 you can use blobs to split a file into small chunks and individually upload each chunk. On completion of each chunk you can update the progress status.

You would need to use Javascript to create a progress bar. A simple Google search led me to this article: WebAppers Simple Javascript Progress Bar with CSS.

Dojo File Upload Progress Bar Widget is another option using the Dojo Javascript framework.

EDIT: Assuming your uploading a large number of images (such as a photo album), and POSTing them to your PHP script, you could use javascript to read the results back from the post and update the progress bar based on the number of images uploaded / total number of images. This has the side effect of only updating after each post has completed. Check out here for some info on how to post with JS.

A php/ajax progress bar can be done. (Checkout the Html_Ajax library in pear). However this requires installing a custom module into php.

Other methods require using an iframe, through which php looks to see how much of the file has been uploaded. However this hidden iframe, may be blocked by some browsers addons because hidden iframes are often used to send malicious data to a users computer.

Your best bet is to use some form of flash progress bar if you do not have control over your server.