Jun 20 2013

Sort observableArray of Objects in Knockout.js

Category: PHP,Programmingksg91 @ 6:32 pm

Lately, I have worked good amount of time with knockout.js and to be honest, I have been quite impressed with the dependency tracking of ko.js , no doubt, performance sucks sometime if you don’t take enough care.

Knockout.js offers a sort method for observableArray which sorts the array alphabetically (for strings) or numerically (for numbers). But consider a case when observableArray is of some objects or say you need to sort the array on some special condition. Just sort() method won’t work.

ObservableArray.sort() methods allows you to pass a function. Your function will be passed two objects and now it is up to your function how to sort them. Your function should return a negative value if first object is smaller (in your term), a positive value if first object is great, zero if both are equivalent.

For example, let’s say you have a observableArray of product object and you want to sort the array based on the price,  you may do something like this

function myCompareFunction(a,b){
  if(a.price()<b.price()){ // if price is observable
    return -1;
  }else if(a.price() > b.price())
    return 1;
  }else {
    return 0;
  }
}
myObservableArray.sort(myCompareFunction);

Similarly, you can sort your observableArrays. It is up to you on how you want to.

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Mar 01 2013

HOW TO STORE A FILE AND MAKE IT DOWNLOADABLE?

Category: PHP,Programmingksg91 @ 8:00 pm

HOW TO STORE A FILE AND MAKE IT DOWNLOADABLE?


I often come across this question and new comers often find it difficult to understand. Let me put this thing in simple way.

What do we need to do this?

To make this possible, we need to do following simple things:
  1. Store file at some permanent location
  2. Store data about file
  3. Serve the file whenever user request for it.
 
If we simply move uploaded file to a particular location, we may end up overwriting a file which was previously uploaded and had same name. To cope with this issue, we may rename the file and try to generate a unique name to avoid collision. 
 
I usually follow following approach:
 
//! Generate a unique file name
 $uniqueFileName == md5(uniqid('',true));
//! Generate a upload path
$uploadfileTo =  UPLOAD_PATH. $uniqueFileName ;
//! Move to permanent location
move_uploaded_file($file['tmp_name'], $uploadfileTo);&amp;lt;br /&amp;gt;

uniqid() generates a random string. First argument is prefix for the random string. If we pass second argument as true, a string with more entropy will be generated , i.e. more random numbers. We are hashing the generated string using md5 algorithm. You can also use the hash of combination of timestamp and output of uniqid().

Now if we have store the file, we will need information of file in our database.  I would recommend storing at least this details about file:

  • File’s original name
  • File’s extension
  • File’s Content-Type / MIME type
  • File Size
  • Storage location
  • File’s generated name
Now when you’ve store this information in database, you can create a download page. This can be achieved in two ways.
  1. Redirect user to the URL of actual stored file.
  2. Create a proxy page which will serve the content of file.
Problem with first approach is that, actual storage URL is known and you have no control over who is accessing it.
 
I will recommend using second approach. To do so, we have to tell browser that the php page is actually an original file with particular content type. Browser identify the document based on the HTTP headers. So, we can achieve this by simply passing proper HTTP headers. PHP allows us to send HTTP headers using function header() .
 
On a download page, you can simply retrieve details of original files. Suppose we have those details in self explaining variables below, we can serve the file using following code snippet:
//! pass content type header for the file
header("Content-type: {$sContentType}");

//! force browser to download the content
header("Content-Disposition:attachment;filename='{$sFileName}'");

//! load the content of the file
readfile($filePath);

And that’s it. Your file will be served to user with original name and content type. And user will actually never know the real location. 

Common issue people face with this is, file is downloaded properly but when they open it, they realized that the file is corrupted. This happens because you are sending some other output to the browser also as payload along with content of file. You may have some code which is echoingsomething.  You can also use output buffering to stop sending anything to browser except the actual content. Use output buffering, before you readfile flush the output buffer and then read the file.


Nov 06 2012

Generating List of affected file from patch files of Git with PHP

Category: PHP,Programmingksg91 @ 8:44 pm

No doubt, Git is a best thing you can use for managing your code. But sometimes you really put yourself in such a worse situation that you start cursing yourself for using Git. I am working on a fairly large project and been working in teams, I had to switch to another branch because the code base I had was greatly differing from the one on git but I had to work with that source because of some reasons. Being base code not being same as Git’s master, I made a commit and started working on that. I cannot simply merge because there were total 20k+ files with code and almost impractical to go through most of them to resolve the conflicts.  I thought of then applying patch for all the later commits. It started giving me lot’s of conflicts too. The files I worked on were not touched by others so simple thing was to take all the files that I edited and to use them. I am no git expert and quite lazy to find the way to do so.  There can be several nice way to deal with this situation using git only but as I said, I am no git expert. And that is not this post is about.

So I created a simple php script that can read and identify the files that were affected in that commits. I thought to share the code, so this is the post.

As I explained already, I had created serial patch I can read from it the affected files. Being quite short on time, wrote a quick code, which may be improved in efficiency and accuracy.

Here is the script I wrote:


<!--?<span class="hiddenSpellError" pre=""-->php
 $result='';
 for($i=1;$i<89;$i++) {
 $fname=glob('patch/'.substr("0000".$i,-4)."*");
 $entry=$fname[0];

 $content = explode('diff --',file_get_contents($entry));
 $content = $content[0];
 $re="/([a-zA-Z0-9_]+)(\.php|\.js|\.css)/";
 preg_match_all($re,$content,$out, PREG_PATTERN_ORDER);
 $out[0]=array_unique($out[0]);
 foreach($out[0] as $val){
 $result[$val]=true;
 }
 }
 foreach($result as $key=>$val){
 echo $key."<br />";
 }

?>

Explanation

Simple thing to do was to read each patch and look for a filename. I used three extensions to look: .php , .js, .css . I put the folder in a directory and put patches in the subdir patch/

Format for patch file name was a serial number starting from 0001 up to the number of files. I simply generated name myself using glob(). I am sure you will argue why didn’t I simply read the directory. Actually, my initial code cause script to exceed the timeout and I was not sure if it was the number of file or something else. So I thought of controlling the number of files. So was the code like this.

Reason for so long execution time was preg_match_all on a long patch files (couple of them were 20 MB! ). We don’t need to search for the files in changes, only portion containing  the list of files was important so I simply search for file names in that portion by exploding contents to diff — and searching in first array value.

To maintain the unique list, I used file name as index so unnecessary memory space does not get wasted. I believe rest of the part makes sense without any explanation.

Above code was enough and efficient in my case. Let me know what you thing about this.

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Jul 19 2012

Transferring Data Securely on HTTP using PHP

Category: PHP,Tips & Tricksksg91 @ 4:23 pm

Image courtesy of MIT OCW.

Well, I have been working on a WordPress plugin and I required to transfer some data from client’s host to my host. Data is Access Token and Secrets for their Twitter account (Of course, not to store it on my host but to perform their operations on Twitter). Being sensitive data, it was required to transfer them securely over the network, keeping it secure from at MITM attacks. As a option, I can use buy a IP and SSL certificate and transfer it using HTTPS. But, being a free plugin, I really didn’t want to spend money in such things. And only option I was left with was to use HTTP and transferring data encrypted.

For this, client will register to me and avail its access token and secret (not of twitter, but for my site). There were multiple data and instead of encrypting them independently, I decided to make a class named Request which holds all the data to be transferred.  Now this request class is serialized and then that string can be encrypted.

I use following code snippet to encrypt :

$req=serialize($this->request);
$req=$this->key.$req;
$this->enc_req = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($this->acc_sec), $req, MCRYPT_MODE_CBC, md5(md5($this->acc_sec))));

Here,

$this->key

is Access key given to user and

$this->acc_sec

is Access Secret given to the user.
Let’s check example of this encryption:

Object Request:

object(Request)[1]
  private 'tmp_key' => string  '___' (length=16)
  private 'tw_acc_tok' => string'blah' (length=4)
  private 'tw_acc_sec' => string 'blah 1' (length=6)
  public 'tweet' => string 'Tweet' (length=5)

Serialized Object

string

 'O:7:"Request":4:{s:16:"?Request?tmp_key";s:16:"___";s:19:"?Request?tw_acc_tok";s:4:"blah";s:19:"?Request?tw_acc_sec";s:6:"blah 1";s:5:"tweet";s:5:"Tweet";}' (length=168)

Encrypted Object

string

 'NxFivVICmrRzh/fSlvT3jeWrT8pdvWRKPPc9lpEe1g1MoYgvom2/Sg6kqm0sqQ/PeYIeJXCahQSubW78CbHzBfMcIXsBCmAistVq/XvkZUSe5Hb5OWIr1D3AiGb5943BO9E2reUKr0GJYyIS+Lxrh1mTvSdpbcu9twt7qqhay6dU77icqu8jdvDBs7XrBTTxDFNS57Cl8KYSICInrJ30nwT8CqLHZdsA4poAhZm7TeIV7xp+bUmRAF5WXV6QUlKm' (length=256)

 Now, this encrypted data is sent to me using cURL and Access Key and encrypted text is send along with it.

On my end, I have access token and secret stored in my database, so I will decrypt the request using the access secret that I have stored in my database with the requesting access token. Following code will help me to recover original Request object:

&nbsp;
<pre>
$decrypted = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($encrypted), MCRYPT_MODE_CBC, md5(md5($key))), "\0");
 $so=substr($decrypted,strlen($this->key)+1);
 $this->request=unserialize($so);

I have used Access Key as a salt. Of course, it’s not the only thing I am going to use to achieve higher security. But I believe, this will be enough to give you an idea of how we can achieve a certain level of security. I am not quite sure how secure this method is, but surely enough for my application.

Please feel free to post your views and comments on this. Hoping, this helped. :)

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Feb 25 2012

How to Track Your WordPress Plugin’s users?

Category: PHP,Programming,WordPressksg91 @ 7:59 pm

Let me clear this straight, this post isn’t about to create WordPress plugin, but how to track your plugin users (blogs).

I have recently published my first plugin on WordPress’ repository at http://wordpress.org/extend/plugins/tweet-my-post/ and I felt really happy to see the downloads. However, what I was missing was, who are using my plugin. I am not sure if tracking the plugin users prohibited or not by WordPress but I am just tracking the url of blogs, that uses my plugin.

Let’s get back to the point – how to track our plugin’s users. This is a simple thing, but main thing is, this should strike your mind. I am posting this for those who haven’t thought (or not able make this happen). Useful also if you’re planning to make one too.

Plugin has a plugin_activation and plugin_deactivation hook, that means, you can register your functions that are executed every time, your plugin is activated and deactivated.

You need to add following code in your plugin file:
As I mentioned earlier, I have added log_operation($op) in the functions that are called while activation and deactivation. $op is operation, either activate or deactivate. Use  appropriate operation in functions. Then whenever plugin is activated or deactivated, log_operation will be called. That function will create a cURL session and post the data of blog url and activation status to the page on our server. Now, what you need to do is to put following code in a page, let’s call it service.php, which is hosted at your server. What it will do is, add the status in our database. You need to put link to this page in above code as a value of $url variable.  
The code is relatively simple to understand so I’m not explaining it at all. Just replace the database name and user details with yours. You will now need the database. Use following table:

Well, you are not ready to see, who are using your plugin. You can look into your database table and enjoy! :D

If you’re lazy to open PhpMyAdmin and browse the database, simply make a file which fetches the data and display it. ;)

I have not added this in my initial release of plugin, so I can only track the users who are using it after Tweet My Post 1.0. Actually, I should be able to track old users too, because WordPress first deactivate plugin, update it and the reactivate it, so I should have the data of old users who have update the plugin but WordPress doesn’t execute activation and deactivation hook while updating plugin. I’m not sure if this is a bug or intentional, but I can’t know my old users unless they deactivate and reactivate the plugin.

Anyways, if you have any problem or query, please let me know in comments below or ping me  @ksg91 on Twitter. :)

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Feb 23 2012

Tweet My Post 1.0 Available

Category: PHP,Programmingksg91 @ 11:11 pm

I have just released an update for Tweet My Post plugin for wordpress. If you are already using it, update it from Plugin menu. You can try plugin by searching for “Tweet My Post” in plugin directory or visit http://wordpress.org/extend/plugins/tweet-my-post/

New version doesn’t have changes to end user but I have updated code internally and added tracking system for me, so that I can analyze plugin usage.

Let me know if you face some problem or issue with this new update. Suggestions are most welcomed.

It’s really nice to see around 400 downloads in just 2 days. Thanks for the support guys. :)

 

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Feb 19 2012

Tweet My Post – A WordPress Plugin

Category: PHP,Programmingksg91 @ 10:16 am

I also run a blog at http://NokiaTips.in and we have many authors there. I always wanted a plugin which auto-tweet our new post to our Twitter account @NokiaTips. There are several WordPress plugin available but I wanted more out of that. I wanted that, that tweet should also contain the twitter handle of Author, so that readers can know that post is authored by whom. I searched WordPress’ Plugin directory but couldn’t find one. So, I thought, better to create one, myself.

I have almost finished the plugin. Find its Git repo at Github – https://github.com/ksg91/Tweet-My-Post

I may have some bug. It’s beta release for now tagged 0.9.

If you have any suggestion, please let me know. You can also contribute to Plugin by forking the repo.

Feel free to try the plugin, after all, it’s free. ;)

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Jan 13 2012

Autolink-Twitter : A WordPress Plugin to Autolink the mentions and hashtags

Category: PHPksg91 @ 3:27 pm

WordPress’ official plugin contains some nice plugins that automatically replace mentions and hashtags with links to the profile and search page. But they also brings other several features. I just wanted a simple plugin which does only this thing. I also wanted to learn making plugins for wordpress. So I thought to make one.

So here is a plugin I named Autolink-Twitter. It links mentions to twitter profile page and hashtags to search stream.

Download Plugin: Autolink-Twitter

How to Install?

Put autolink-twitter.php file under your plugin directory and activate plugin from your admin menu.
I haven’t uploaded the plugin yet to wordpress.org library because I think very few people would be interested there.
You may keep up with this plugin on my Git repository on github at https://github.com/ksg91/Autolink-Twitter


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Dec 24 2011

Simple Function to Delete Files Matching a Pattern in Directory and sub-dir

Category: PHP,Programmingksg91 @ 2:31 pm

Today, a guy was asking for a small PHP function to delete all files which match a pattern in a particular directory and all it’s sub-direcory . So I wrote following simple function which uses stack to keep track of unvisited directory. It is similar to Depth-First-Search approach for traversing nodes in a tree.


<?php 
function removeFiles($dir,$pattern)
{
  $stack=array();
  array_push($stack,$dir);
  while(true){
    $dir=array_pop($stack);
    if($dir==NULL)
      break;
    $a= glob($dir.'/'.$pattern);
    foreach($a as $file) {
      if(is_dir($file)) {
        array_push($stack,$file);
        continue;
      }
      unlink($file);
      echo "File: ".$file." has been removed.
";
    }
  }
}
?>

Let me know if there is any improvement I can do on this code. :)