Ownership and Borrowing in Rust

I’ve been having a lot of fun learning Rust. I’ve been going through the second version of the Rust book and have covered uptil chapter 6 – Enums and Pattern Matching.

One of the unique things about Rust is the Ownership system. I had some doubts understanding this. Searching on Google lead me to this little website – http://intorust.com/ that has some really cool videos explaining – ownership and borrowing.

The author, Nicholas D. Matsakis, has a lot of other interesting work that you can read at http://smallcultfollowing.com/babysteps/

On another note, I’ve been pushing my Rust code to the repository here. I’ll be happy to receive any feedback.

Handling JSON request in PHP

I’ve been working with PHP and jQuery AJAX quite a bit lately. Along with sending form data to PHP page through AJAX, I’ve written restful web services in PHP that receive data in JSON format.

In general when you are sending data through jQuery AJAX to PHP, you don’t have to specify a contentType. Depending on your type ‘GET’ or ‘POST’, PHP will nicely wrap your content into either the $_POST or $_GET global arrays. When you don’t specify a contentType the default contentType is taken as application/x-www-form-urlencoded; charset=UTF-8’.

Following is the request headers from an AJAX call without contentType specified,

To further test this, I set up the following PHP code on my server,

The response that for the above request case was,

If we put the jQuery AJAX type property as ‘POST’ we will have the following request header,

Nothing much changes. The action is specified as POST and the data is no longer a part of the request header. The response from the server is following,

Obviously, PHP has no issues parsing content of type – application/x-www-form-urlencoded; charset=UTF-8. As soon as it sees that contentType, it checks the action and packs the data nicely into either $_GET or $_POST.

Let’s now talk about JSON data. In general, restful web services accept data of type JSON. When sending data via JSON the contentType for jQuery AJAX is application/json; charset=UTF-8

This is the request header,

When PHP receives this data and looks at the content type, it’s not quite sure how to process it, so it leaves it alone. In this case the action – ‘POST’ or ‘GET’ doesn’t matter. You’ll notice that $_POST or $_GET both, are empty arrays. Now, it’s up to you to read this data and parse it.

The code above, reads the data from PHP’s input stream. Since we have passed a JSON string, we decode it, which converts it to a PHP array and stores it in $app_json. If the data you send is not in a correct JSON format, $app_json will have false.

When we echo our response, we get the following on the client side,

I set up a small project to illustrate what has been written here. You can find it over on my github page.

get_results PHP function not working on CentOS

There are instances where the PHP function – get_results will not work on CentOS (this maybe the case with other Linux based operating systems as well). I faced this issue while deploying a project on CentOS which was originally developed on Windows. All my INSERT, UPDATE and DELETE database statements were working properly, but bulk SELECTstatements had issues. Closer inspection narrowed down the problem to the get_results function.

I came across this on the get_results PHP documentation page –

I was able to determine if mysqlnd driver was installed using this post on StackOverflow as reference. As expected, it wasn’t.

Here’s the relevant php code from the StackOverflow post –

Now that I new that we needed to install the mysqlnd driver, here are the steps that I followed to get the mysqlnd driver working on CentOS,

After installing the mysqlnd driver the get_results function worked just fine.

Tree view based file explorer for the web using jQuery.

This post assumes that the reader has a basic understanding of PHP, jQuery and jQuery $.post

Recently I had to implement a windows-esque tree view based file explorer for one of my projects at work. I ended up using this wonderful jQuery plugin to help me. In this blog I’ll be going through some basic code to get it working using PHP on the server side.

To whet your appetite, here’s what we’ll be achieving in this blog post – A complete tree view based file explorer that feeds from a folder on the server’s file system.

File tree view

So let’s get started!

To be able to render a proper tree using the aciTree plugin, we’ll need to send JSON from server in the following format –

Here’s the list of things that we’ll be doing –

  1. Server Side Code
  2. HTML
  3. JavaScript/jQuery code to communicate with the server.
  4. Basic event handling for the aciTree plugin.

1. Server side code

Let’s move onto the PHP code. Our job is to read the files from the specified folder and return a JSON structure that resembles what’s shown above. If you look closely you’ll observe that the JSON above is basically an array of objects of with properties as – id, label, inode, icon, open

The following class is exactly similar to that of the class received via JSON. We’ll be returning an array of NodeList objects from the server.

Now to read the list of files and folders from a location on the server –

Some code to handle the request that we will be making from the client side and then echoing the output in JSON format –

Okay so we have the PHP code in place. Next order of things –

  1. Server Side Code
  2. HTML
  3. JavaScript/jQuery code to communicate with the server.
  4. Basic event handling for the aciTree plugin.

2. HTML

The following HTML goes inside the body tag-

Next, the JavaScript/jQuery to get the aciTree plugin working. This should be put inside the document’s ready handler –

3. jQuery code to communicate with the server

4. Event handling for the aciTree plugin

And finally a simple event handler for the aciTree that is triggered whenever a node in the tree is selected –

You can find the whole code here and a working copy of the project here.

Passing JavaScript object to ASP.NET web service or method

I recently came across a question on StackOverflow, where the author was having trouble calling a JSON based web service from his ASPX page using jQuery. He was passing a user defined JavaScript object. I decided that I would quickly put a project together describing how to do so, for my future reference, and for anyone else who needs help. Here is my original answer on StackOverflow. I’ll be offering a higher level of explanation here in the post.

Below is the web method that we’ll be calling, in my ASPX page code behind. Note that a web method has to be declared as static,

The user defined object that you pass through JavaScript has to have the same properties as the user defined object on the server. Say for example that you were passing the following from JavaScript –

The object we defined in JavaScript has two properties, name and phone in lower case letters.

This is exactly similar to the class defined on the server

Note that the properties in the class have to be public

Now we’ll see how to call this web method from our ASPX page,

For an explanation of the options used here check jQuery ajax API documentation,

I’ll be discussing two noteworthy things,

1. Sending data to the server

Data (data) contains the object we will be sending to the server. Before we send the object to the web method, we have to ensure that we convert the object into a JSON format. We can do this by calling JSON.stringify. This javascript method is supported in all modern browsers*. The values that you pass to JSON.stringify have to be similar to what I have specified here. The name of the object we are passing to the server is named as 'cnt' in single or double quotes. This also has to be exactly same as the variable name being accepted by the web method.

2. Specifying what to connect to

The url specifies the web method or web service that we wish to call. If we were calling an ASP.NET based web service, we’d just have to change the url to /Default.asmx/getContact. Note that the name of the method that we wish to call is concatenated to the end of the web service path.


Now let’s see everything in action using Fiddler, a nifty network monitoring tool.

You’ll notice the call, with the request data sent to the server, and the response that is received from the server. If the call succeeds the success function of jQuery ajax is called. The server returns data as a JSON object and we can access it using the d property of the object. ASP.NET adds the property by default as of .NET Framework 3.5 to protect you from JSON hijacking.

Data sent to the server

Response from the server

So that’s basically it, if you have any doubts, ping me through the comment section. You’ll find the source code for the application here.

JSON.stringify is not supported by Internet Explorer 7 by default. To add this function to it, add JSON2.js to your page.