GWT Blog – GlobalWorldTech

Now a days most of the websites are database driven, we have seen that many websites show data as a long list. Well, there is nothing wrong in that but if you have to find any information in that long list, it will be quite tedious and painful activity.

We think that the best way to present data is, by using Page numbers, easy to surf and finding information wont take any time, as the surfer can go directly to the desired page and find the relevant information.

Creating page numbers can be a difficult thing if you are using a procedural way of coding. But if you are using CodeIgniter, creating page numbers can be as easy as a child’s play. CodeIgniter is an application Framework that uses MVC architecture, which allows great separation between Logic and Presentation.

Here is all you need to do:

$this->load->library(‘pagination’);
$config['base_url'] = ‘http://www.gwtindia.com/index.php/test/page/’;
$config['total_rows'] = ’200′;
$config['per_page'] = ’20′;

$this->pagination->initialize($config);
echo $this->pagination->create_links();

The $config array contains your configuration variables. It is passed to the $this->pagination->initialize function as shown above. Although there are some twenty items you can configure, at minimum you need the three shown. Here is a description of what those items represent:

base_url : This is the full URL to the controller class/function containing your pagination. In the example above, it is pointing to a controller called “Test” and a function called “page”. Keep in mind that you can re-route your URI if you need a different structure.
total_rows : This number represents the total rows in the result set you are creating pagination for. Typically this number will be the total rows that your database query returned.
per_page : The number of items you intend to show per page. In the above example, you would be showing 20 items per page.

The create_links() function returns an empty string when there is no pagination to show.

**Note: Please change the base_url to your website / application url **

Model–View–Controller (MVC) is a software architecture, currently considered an architectural pattern used in software engineering. The main aim of the MVC architecture is to separate the business logic and application data from the presentation data.

1) Model: The model object knows all about the data, that is needed, to be displayed. It is the model who is aware about all the operations that can be applied to transform that object. It only represents the data of an application. The model represents data and the rules that govern to and updates of this data. Model is not aware about the presentation data and how that data will be displayed to the browser.

2) View: The view, as the name suggest, represents the presentation of the application. The view object refers to the model. It uses the query method of the model to obtain the contents and renders it. The view is not dependent on the application logic. It remains the same even if there is any change / modification in the business logic. In other words, we can say that it is the responsibility of the view to maintain the consistency in the presentation.

3) Controller: Whenever a user send a request, it always go through the controller. The controller is responsible for intercepting the requests from the view and passes it to the model for appropriate action. After the action has been taken on the data, the controller is responsible for directing the appropriate view to the user. In GUIs, the views and the controllers often work very closely together.

How MVC work in Web Development

• First, the browser send an HTTP request to the web application.
• A dispatcher usually will get this HTTP request and determine which controller to be used. This dispatcher is usually called a Front Controller.
• The controller will receive it and from the data received, determine which model’s are needed, what data is required and what actions are needed on the data.
• The model will retrieve the data and implement any necessary actions. Then, it will return the results to the controller, successful or not.
• The controller, based on the results from the model, will then determine which view should be used and provide the view whatever data is to be published to the browser.
• The view will receive this data, implement any presentation logic to the data, and return it back to the controller.
• The controller will then return the results to the browser.

Currently, there are many Frameworks that uses MVC Architecture, popular being Spring MVC Framework, Struts, WebWork, Swing, SproutCore, JavascriptMVC , eMVC, ASP.NET MVC Framework, CakePHP, CodeIgniter .. etc.

If you use CodeIgniter for your development, you often come to a point wherein you ask yourself – How to create user friendly URLs? In this post, we will tell you, how you can create User friendly URLs through CodeIgniter. But first we need to understand how CodeIgniter creates the URL and the approach that it follows.

CodeIgniter uses a segment-based URI approach rather than the conventional standard “query string” approach to URLs.

What are URI Segments?

The segments that represents the URL e.g. example.com/class/function/ID

• The first segment represents the controller class that should be invoked.
• The second segment represents the class function, or method, that should be called.
• The third, and any additional segments, represent the ID and any variables that will be passed to the controller.

We can remapped the URL , how we want using the URI Routing feature. The URI Class and the URL Helper contain functions that make it easy to work with our URI data.

Adding a URL Suffix

In config/config.php file we can specify a suffix that will be added to all URLs generated by CodeIgniter. For example, if a URL is this:

example.com/index.php/products/view/mobile

We can optionally add a suffix, like .html, making the page appear to be of a certain type:
example.com/index.php/products/view/mobile.html

Enabling Query Strings

CodeIgniter optionally supports this capability, which can be enabled in application/config.php file. If you open your config file you’ll see these items:

$config['enable_query_strings'] = FALSE;
$config['controller_trigger'] = ‘c’;
$config['function_trigger'] = ‘m’;

If you change “enable_query_strings” to TRUE this feature will become active. Your controllers and functions will then be accessible using the “trigger” words you’ve set to invoke your controllers and methods:
index.php?c=controller&m=method

URI Routing: Setting your own routing rules

Routing rules are defined in application/config/routes.php file. You’ll see an array called $route that permits you to specify your own routing criteria. Routes can either be specified using wildcards or Regular Expressions

1. Wildcards – There are two types of wildcards are used

• :num – :num will match a segment containing only numbers.
• :any – :any will match a segment containing any character.

A typical wildcard route might look something like this:
$route['product/:num'] = “catalog/product_lookup”;

In a route, the array key contains the URI to be matched, while the array value contains the destination it should be re-routed to. In the above example, if the literal word “product” is found in the first segment of the URL, and a number is found in the second segment, the “catalog” class and the “product_lookup” method are instead used.

Here are a few routing examples:
$route['blog/sat'] = “blogs/users/34″;
A URL containing the segments blog/sat will be remapped to the “blogs” class and the “users” method. The ID will be set to “34″.

$route['product/:any'] = “catalog/product_lookup”;
A URL with “product” as the first segment, and anything in the second will be remapped to the “catalog” class and the “product_lookup” method.

$route['product/(:num)'] = “catalog/product_lookup_by_id/$1″;
A URL with “product” as the first segment, and anything in the second will be remapped to the “catalog” class and the “product_lookup_by_id” method passing in the match as a variable to the function.

2. Regular Expressions – We can use regular expressions to define routing rules. Any valid regular expression is allowed. A typical RegEx route might look something like this:

$route['products/mobile/([a-z]+)/(\d+)’] = “$1/id_$2″;
In the above example, a URI similar to products/mobile/123 would instead call the mobile controller class and the id_123 function.