Feedburner: Adding Flattr to your FeedFlare

Update 2010-06-11: This article and information with-in are superseded by Feedburner: Adding Flattr to your FeedFlare (Part: 2)

I've added Flattr to my blog and also wanted to add it to my feedburner FeedFlare, but alas, no one has yet to create one. So I've gone through the trouble of doing it for you :)

First, I went to the Feedburner FeedFlare API documentation. I wont go into the details of writing your own flare, but I opted for the dynamic type, since it would allow me to show how many times one of my blog posts had been flattered.

Second, I dove into the Flattr JavaScript API. I don't think they recommend this, but it's the only way I could get to the button information contained in their default IFrame.

Third, I downloaded the PHP Simple HTML DOM Parser. There's probably a simpler way to parse the IFrame sent back from Flattr, but I opted for this method since it was pretty straight forward.

For the lazy, you can use my existing FeedFlare URLs as your own. You will need to go to your feedburner page, login, select the feed you want to add this to, click on "Optimize" and then "FeedFlare". Below the stock list you will see a place to enter a URL. Enter the URL below and BE SURE to replace "your_uid" with your Flattr UID, else you wont get the money.

http://www.swissdisk.com/~bcollins/flattr-me-dynamic.php?uid=your_uid

For the interested, here are the two files I've created. First is the dynamic PHP FeedFlare file:

<FeedFlareUnit>
  <Catalog>
    <Title>Flattr Me</Title>
    <Description>
      Adds a Flattr link including flattr count for each feed unit.
    </Description>
    <Link href="http://www.swissdisk.com/~bcollins/flattr-me-dynamic.php?uid=flattr_uid"/>
    <Author email="benmcollins13@gmail.com">Ben Collins
  </Catalog>
  <DynamicFlare href="http://www.swissdisk.com/~bcollins/flattr-me-static.php?uid=<?
        print $_GET['uid']; ?>&title=${title}&link=${link}"/>
  <Sample>Flattr (11)</Sample>
</FeedFlareUnit>

Note that the <Link> element references another PHP script, and that this is in fact PHP. This allows us to pass along the Flattr UID to the second script, which is the one that actually produces the FeedFlare (feedburner periodically checks the second URL it gets from this file for updates to the FeedFlare).

Now, the second script is the one that uses the simple_html_dom.php library I spoke of. You will see it referenced in the file below. Basically I pack the data just like the original Flattr load.js script does, and request the Flattr button, and then rip a few bits of information from it:

<?
include_once("simple_html_dom.php");

$btn_url = "http://api.flattr.com/button/view/";

$data = "button=compact&uid=" . $_GET['uid'] .
        "&url=" . $_GET['link'] . "&lng=en_US&hide=0&title=" .
        $_GET['title'] . "&cat=text&tag=&desc=";

$html = file_get_html($btn_url . bin2hex($data));

$els = $html->find("span.flattr-count");
$count = $els[0]->innertext;

$els = $html->find("a.flattr-pop");
$link = $els[0]->href;

$els = $html->find("span.flattr-link");
$txt = $els[0]->innertext;

?>
<FeedFlare>
  <Text><? print "$txt ($count)"; ?></Text>
  <Link href="<? print $link; ?>"/>
</FeedFlare>

Those familiar with Flattr will note that I did not pass in the description, which could probably be added in the first script (or at least a shortened version of it) and then passed to the button. Usually the description is the first few hundred characters of the post in this case.

Hope all works well. Please post back if you take the time to add the description to this!

PHP: Sending Motion-JPEG

As you may know from past posts, I was trying to send Motion-JPEG from a PHP script. This proved (for many reason) not so easy. After I conquered writing php extension modules, I was still left with nuances in PHP that made it difficult to send MJPEG from my script.

Here's the basic run-down of difficulties:

• PHP buffers output to the client and this keeps you from doing continuous streams of data easily
• PHP doesn't allow you to send headers after it thinks the headers have already been sent
• Apache has some other handlers that also cause buffering
• Apache does some client negotiation that conflicts with MJPEG (mod_gzip)

Searching the Eentarnets did not produce good results on how to handle this. At least, not in a single place and easily findable. So here's my solution for others to use:

<?
# Used to separate multipart
$boundary = "my_mjpeg";

# We start with the standard headers. PHP allows us this much
header("Cache-Control: no-cache");
header("Cache-Control: private");
header("Pragma: no-cache");
header("Content-type: multipart/x-mixed-replace; boundary=$boundary");

# From here out, we no longer expect to be able to use the header() function
print "--$boundary\n";

# Set this so PHP doesn't timeout during a long stream
set_time_limit(0);

# Disable Apache and PHP's compression of output to the client
@apache_setenv('no-gzip', 1);
@ini_set('zlib.output_compression', 0);

# Set implicit flush, and flush all current buffers
@ini_set('implicit_flush', 1);
for ($i = 0; $i < ob_get_level(); $i++)
    ob_end_flush();
ob_implicit_flush(1);

# The loop, producing one jpeg frame per iteration
while (true) {
    # Per-image header, note the two new-lines
    print "Content-type: image/jpeg\n\n";

    # Your function to get one jpeg image
    print get_one_jpeg();

    # The separator
    print "--$boundary\n";
}
?>

That's it in a nutshell. Make sure that your PHP script does not contain any newlines or data before or after the PHP enclosures (<? ... ?>).

The joy of writing a php5 module

As a follow up to my last post, I wanted to give a quick update.

As it turns out, I ended up writing a php5 Zend module to wrap up some functions I use to access v4l2 devices. I have to say that writing a php5 module was pretty straight forward. Big thanks to the Extension Writing tutorial I found, which was well written, and did not leave me with any questions.

I was able to get the module ready in a few hours, and spent the rest of this morning cleaning it up and tweaking it a bit.

Now I'm completely able to read my v4l2 devices and mjpeg stream them from my PHP script :)

Request-for-help: PHP and Video4Linux

As it turns out, I do not like writing web applications. Give me registers and DMA, keep the CSS and JS...thanks.

Anyway, I have to find a way to feed an MJPEG output from a PHP script. WAIT! I know this sounds easy, and if not for all the caveats of what I have to adhere to, it would be very simple...maybe.

It seems that PHP doesn't have a way to use ioctl()'s. I can open() a v4l2 device just fine, and read() from it with ease, but your SOL if you want to do something cool with that file handle in PHP.

I need to be able to do ioctl()'s because my v4l2 device requires at least one so I can put it into MJPEG format (as opposed to the default MPEG format). I can serve up these JPEG/MJPEG's through apache perfectly using a C program I've written.

However, I have to use PHP because the rest of the web application is written in PHP and there is already authentication mechanisms storing credentials in PHP sessions. I don't want to have to parse PHP sessions in a C program.

The normal method I found for doing JPEG from a PHP script worked like this:

<?
header("Content-Type: application/jpeg");
passthru("/usr/bin/grabjpeg");
?>

This works perfectly. Except I want to be able to do a MJPEG feed which requires sending one image after the next with headers in between. PHP doesn't like this much, nor does it like the fact that I want all of these headers to come directly from my C program and not from the PHP script. I also do not want to call grabjpeg for each frame, since that's too much overhead in between frames.

What ends up happening is that my headers from the C program are sent as part of the content that the client thinks is the JPEG file.

Right now, I can only see one way to handle this, and that's to write a PHP module to expose libv4l, but I'm open to suggestions on being able to call an ioctl() from within a PHP script.

Dear Users: Do not withhold information from developers, kthxbye

I accidentally stumbled upon a debugging case today with a user that seems to be a common problem. I wont call this user out directly, but he was a case study in what not to do when you want help from a developer like myself.

The basic volley started off with the usual chit chat in an IRC channel:

<User> Can someone help me compile a module for my kernel?
<Me> Sure, what seems to be the trouble?

So off we went with some IRC and PasteBin exchanges of his compile problem. I looked at the source code for the driver he was trying to compile, and it was a one-line obvious fix to get it working with a newer kernel such as the one found on the Ubuntu 10.04 Lucid system he was working on.

So now the module compiled, and he tried loading it. Hmm...the module disagreed with symbols from modules on his running system, videodev to be exact.

Weird. That shouldn't happen. I asked him if he had compiled or installed different versions of v4l than what his system came with. He didn't recall. However, after getting him to pastebin "ls -lR" of his modules directory, it was apparent that 3 days ago, he did in fact completely replace the drivers/media install.

This meant that those modules didn't match the stock headers that came with his running kernel. This took a very short time for him, but considerable time for me (volunteer time) to find out. After finding out, he admitted to replacing the modules.

Now it was obvious that he was embarrassed to admit he had junked up his system, and even more embarrassing that I caught him in a lie. He could have saved time for both of us. If I had given up after helping with his initial problem, he would have been stuck not knowing how to fix it.

So the moral of the story here is, don't hide information from people trying to help you. Tell all the gross details. If you fed your cat buttermilk waffles off your keyboard, it might help to know that if your 'H' is stuck.