My struggles in understanding and learning about Object Oriented design, and the tools and knowledge I've taken from them.

Monday, February 7, 2011

PHP Code that Looks like .Net code

This blog references PHP files available for download here: Click Here

In programming, I think it's important to learn. Learning can involve new aspects of your chosen language, or new languages. I've been thinking about my PHP days lately. I really know a lot more about programming now then I did when I was actively programming in PHP.

When I go back and look at some of the code I was producing in PHP, I cringe a bit at all of the principles I see myself violating. Most of the PHP code I wrote were big balls of mud.

So, as an academic experiment, as well as to try to re-sharpen some of my PHP skills, I decided to write some base libraries that I may (or may not) eventually use someday.

As with any language (programming or verbal), or with any foreign concept, the first thing to do is to find metaphors that allow us to relate the themes of the thing we're learning to the things we already know. The classic example in programming is the Hello World application.

Well, I'm not too interested in creating a "Hello World" for PHP, because I'm already familiar with a little bit of how PHP works. But what I wanted to do was to build some PHP code that looks (at least a little bit) like .Net code.

So, after thinking a little bit about what libraries I use most in .Net, I centered around System.Data, in particular DataTable (and DataRow, DataColumn, DataRowCollection, and DataColumnCollection). I haven't created DataSet yet, because there's only so much time in the day.

After thinking a bit more about how I would build some of this PHP code that looks like (has a similar interface) the System.Data .Net library, I concluded that I wanted to have a base Collection object. So I created it, and put it into a file called System.Collections.php. Below is a diagram of the code I created:



As you can see, in my PHP code, a DataTable has a DataRowCollection and a DataColumnCollection, as well as a couple of the external interface behaviors of .Net System.Data.DataTable (NewRow() and AddRow()); however, because of core differences between C# (or I guess .Net languages) and PHP, there are a few changes. Below are the issues that I encountered in this mini-project:

1. I couldn't figure out if I could use an indexer type property to have square brackets ([]) to represent an indexed item in a collection. Therefore, I left that for later.

2. There are some pretty serious differences between C# and PHP in terms of how they type variables. In C#, generally you generally define a variable as a type on the left side of the variable name, and you initialize it on the right side (eg int a = 3; OR Person p = new Person()). You don't have to do that in PHP, so you can initialize a variable as any type, which throws a bit of a wrench into the model of how I see the world.

3. PHP (at least 5.0) supports a lot classic OOP concepts such as inheritance, interfaces, polymorphism, Exception handling, etc. Obviously, the syntax of how to do this is different than it is in C#, so I dealt with some of the pains of the languages' differences.

4. PHP (from my understanding) does not support generic variables. So I can't use List variables the way I like to in C#. So, that's why DataRow and DataRowCollection both inherit from my Collection class.

But, I think my finished product gives me a basis to build on for later. So, if I wanted to initialize a DataTable in PHP code, I would include a reference to System.Data.php, and do something like below:
 
include 'System.Data.php';


$dt = new DataTable();
$dt->AddColumn("FirstName");
$dt->AddColumn("LastName");
$dt->AddColumn("Age");


$dr = $dt->NewRow();
$dr->AddValue("FirstName", "Tim");
$dr->AddValue("LastName", "Claason");
$dr->AddValue("Age", 29);


$dt->AddRow($dr);

Notice in the above that, unlike c#, I can't do $dr["FirstName"]. Maybe there's a way to do this in PHP, but in my (short) research time, I didn't find it.

Obviously, this interface isn't exactly the same as .Net's System.Data, but it's close enough to give me a decent metaphor between PHP and C#.

Please note that I haven't tested this code yet, so there are no guarantees as to whether or not it works. If it does work, expect more blog entries on this topic.

To download the PHP Code I've got so far, Click Here
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