Facebook: Check if user clicked Like page button(just liked the Facebook page)

Very often Facebook applications have "Fangate" page, meaning that if user hasn't liked the page and if he opened application - he can see application page with text something like "Please like our Facebook page before using the app" and can't use the application until he is not page fan.

Our clients as usual ask us to track how many users liked the page from the application.

Signed request contains an information about if user like a page:

$facebook = new Facebook(array(
    'appId' => $app_id,
    'secret' => $app_secret,
    'cookie' => true
));

$signed_request = $facebook->getSignedRequest();
$like_status = $signed_request["page"]["liked"];

So, the challenge is to catch the moment when user clicks like button.

The simples way is to store like status to the session. But it doesn't work in Safari, for iframe Facebook applications Safari doesn't accept cookies and user session is lost.

Nowadays most of polar browsers support local storage. So we can use it to store like status information. Example of source code is pretty simple.

This code example should be in template that is rendered if user is a fan of Facebook page:

<script type="text/javascript">
    if ('localStorage' in window && window['localStorage'] !== null) {
        if (localStorage.getItem('liked_state') == 0) {
            // we've go it: user just clicked like button
        }

        localStorage.setItem('liked_state', 1);
    }
</script>

Pretty simple, isn't it?

Soundcloud API: PHP SDK issue

I tried to fetch track info from the Soundcloud service using 'resolve' method. Code looks like next:

// create a client object with your app credentials
$client = new Services_Soundcloud($clientId, $clientSecret);

// resolve track URL into track resource
$track = json_decode($client->get('resolve', array('url' => $url)));

And I've got fatal error:

Fatal error: Uncaught exception 

'Services_Soundcloud_Invalid_Http_Response_Code_Exception' with message

'The requested URL responded with HTTP code 302.'

in /path-to-project/Services/Soundcloud.php:942

Seems that CURL doesn't follow redirects. It is possible to fix this by setting certain CURL option in Soundcloud class. I've added next to class constructor(line 234):

$this->_curlOptions[CURLOPT_FOLLOWLOCATION] = true;

After that everything started working like a charm.

Problem is already discussed on project google group, so I think the fix will be added to the project repo on GitHub soon.

Nginx error: 502 Bad Gateway. ZF2, APC and segmentation fault.

I tried Zend Framework 2 for my last project. When everything was done with development I moved project to production server but every time I tried to open project url in bowser Nginx returned an error:

502 bad gateway

Server is running under Debian, also I have installed Nginx(1.2.6) + PHP(5.3.20) and PHP-FPM.

Increasing buffer size and read timeout value in Nginx config had no results, still 502 error. I've looked into Nginx logs and found next entries:

… recv() failed (104: Connection reset by peer) while reading response header from upstream ...

So, it seems that problem is not in Nginx config. Something is wrong with backend. PHP-FPM log contains plenty of entries like next:

php5-fpm.log:
WARNING: [pool www] child 7050 exited on signal 11 (SIGSEGV) after 14.101753 seconds from start

Well, something is causing segmentation fault. I'm hosting a lot of projects on this server and everything was fine, problem appeared only for the last project that was developed using ZF2.

Googling a little bit, I found that some of PHP extensions can cause segmentation fault. One by one I started disabling PHP-extensions. After I disabled APC extension problem disappeared and everything started working fine. So, disabling APC extension helped to solve the problem and seems that ZF2 has some problems with APC, or APC has some problems with ZF2 :)

Will try to make some research what exactly was the reason of this problem and post here if I'll find something interesting.

ZF2: Get db adapter without service locator usage

The problem is: I need to get the instance of TableGateway directly, not via service locator. TableGateway object requires configured dbAdapter object passed to gateway constructor.

Next solution can help with this problem:

1. Use GlobalAdaperFeature as static storage for dbAdapter:

use Zend\Db\TableGateway\Feature;


$feature = new Feature\GlobalAdapterFeature();

2. Add bootstrap method to module config:

public function onBootstrap($e)
{
    // set static adapter for all module table gateways

    $serviceManager = $e->getApplication()->getServiceManager();

    $dbAdapter = $serviceManager->get('Zend\Db\Adapter\Adapter');

    Feature\GlobalAdapterFeature::setStaticAdapter($dbAdapter);
}

3. Now it is possible to get access to already loaded dbAdapter object in TableGateway constructor:

public function __construct()
{
    $this->featureSet = new Feature\FeatureSet();

    $this->featureSet->addFeature(new Feature\GlobalAdapterFeature());

    $this->initialize();
}

So we have dbAdapter injected into gateway constructor. Ofcourse, it's not best practice, but this allows to add some flexibility to your application, and anyway object dbAdapter was instantiated via service locator, but only once for all tableGateways on the stage of module bootstraping.

Zend Framework 2: Disable layout rendering

In ZF1.x we have method for disabling layout rendering that looks like:

$this->_helper->layout()->disableLayout(); 

Of course in ZF2 this method doesn't work but there are some other ways how it is possible to do:

1. Set viewModel as standalone model in controller action:

public function someAction() {
    $viewModel = new ViewModel(array(
        'foo' => 'bar'
    ));

    $viewModel->setTerminal(true);

    return $viewModel;
}

2. Create empty layout and use it in controller action:

Create almost empty layout: module/MyModule/view/layout/empty.phtml with only content:

<?php echo $this->content; ?>

Then use this layout in controller action:

$this->layout('layout/empty');

3. Use response object for output content:

$response = $this->getResponse();
$response->setContent("Some content"); 
return $response;

That's all. May be there are some other ways to do this. As for me I prefer the first way, it looks simple and clean.

Mount Amazon S3 storage as local filesystem on Ubuntu server

Amazon S3 is a high reliability online storage. We have recently started using Amazon S3 in our company as a backup storage for our projects and as a storage for static sites content. Next step-by-step tutorial describes how to mount S3 bucket as a local filesystem using FUSE-based file system s3fs.

1. Install neccessary packages

$ sudo apt-get update
$ sudo apt-get install build-essential libfuse-dev fuse-utils libcurl4-openssl-dev libxml2-dev mime-support

2. Next step is to download archive with latest version of s3fs

$ wget http://s3fs.googlecode.com/files/s3fs-1.61.tar.gz
$ tar xzvf s3fs-1.61.tar.gz

3. Compile sources

$ cd s3fs-1.61/
$ sudo ./configure
$ sudo make
$ sudo make install

4. Allow other users have access to s3 bucket that will be mounted

Edit file /etc/fuse.conf with any text editor, I used vim for this:

$ sudo vim /etc/fuse.conf

And uncomment the following line in the conf file:
...
#user_allow_other

5. Add pare of you Amazon account key id and account access key to /etc/passwd-s3fs file

Edit file /etc/passwd-s3fs and add here string: AWS_ACCESS_KEY_ID:AWS_SECRET_ACCESS_KEY
Where: AWS_ACCESS_KEY_ID -- your amazon account key id
AWS_SECRET_ACCESS_KEY -- your amazon account access key

6. Set permissions to file

$ sudo chmod 0600 /etc/passwd-s3fs    

7. Mount s3 bucket to local filesystem

$ sudo s3fs your_backet_name -o use_cache=/tmp -o allow_other /mnt/s3storage

That's all and now S3 bucket can be used as local filesystem.

Facebook Javascript SDK: Security error "Permission denied" in IE while login

Facebook platform is really not friendly with IEs browsers and I'm sure that a lot of developers have many difficulties in IE while working with Facebook. Recently I've faced a troubles in IE7 and IE8 while calling method FB.login(); Authentication popup appears but after that security error popup is shown with text like:

Message: Permission denied
Line: 22
Char: 4250
Code: 0
URI: https://connect.facebook.net/en_US/all.js

In other browsers everything works fine. There is a hack that allows to avoid this error in IE. It is necessary to add some piece of code after calling FB.init() on client side:

  FB.init({
    appId:        'xxxxx',
    appSecret:    'xxxxxxxxx',
    status:        true
    cookie:        true
  });
  // this code solves the issue
  FB.UIServer.setLoadedNode = function (a, b) { 
    FB.UIServer._loadedNodes[a.id] = b; 
  };

The trouble is described in Facebook Bugzilla: http://bugs.developers.facebook.net/show_bug.cgi?id=20168 Hope, it will be fixed by Facebook soon.