What is the default URL pattern used in Codeigniter framework ?

Codeigniter framework URL has 4 main segments in default url pattern. First we have the server name and next we have the controller class name followed by controller function name and function parameters at the end. Codeigniter url segments can be accessed using the url helper. Sample URL is given below.
http://servername/controllerName/controllerFunction/parameter1/parameter2.

What is Codeigniter URL Routing ?

Routing in codeigniter means that we can customize the default URL pattern to use our own url pattern according to our requirement. Once configured whenever request comes and matches our url pattern it will direct to the specified controller and function automatically.

Why we need to change the URL routes ?

How can we define custom routing rules?

Codeigniter provides a file called routes.php located at the config folder to define custom routes to your application.

Removing the controller class name from URL ?

This is effective when you have only one controller with all the functions. Since there is only one controller you can include the function name and parameters in the url and redirect to the available single controller by configuring settings in routes file. Including the following code line in routes files will redirect all requests to controller called “Blog”.

http://www.example.com/functionName/parameters

$route['(:any)'] = "blog/$1";

Requests with any function name is directed to the appropriate function in blog controller. $1 will contain function name and function parameters.

Removing the controller class and function name from URL ?

This is very useful if you are developing a cms with codeigniter. URL’s in cms should be user friendly and seo friendly. We normally maintain the page name of a cms as the parameter. We can optimize pages for search engines if we include the page name right after the domain name. This can be achieved by using routes in CI to remove both controller and function from url.

http://www.example.com/pageName

$route['(:any)'] = "blog/display_page";

All the url’s contain the page name only. So all the pages will be directed to display_page function of blog controller. If you are using this code you can only call one controller and one function name. If you have other controllers to call you have to setup routing rules for them before using above code.