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CodeIgniter URL's are search engine friendly and user friendly. CodeIgniter using segment based approach rather than query string. But it supports query strings, you can optionally enable it.
URI segments:
CodeIgniter follows the Model- view-Controller approach, so the segments of the URI also follows the same. For example -mywebsite.com/article/health/8
. The first segment is the controller class. The second one is the method in that controller. The third one is the Id, the parameter which required for that function.