Library vs. Controller

[eluser]pankaj[/eluser]
lets assume that we don't have a validation library then what you will do for validation you will write all your validation code in you corresponding controller. and this will be a mess if you add hole validation code in one controller. that's why why libraries are created so that you don't need to do all coding in your controller and besides that you can access that libraries throughout your application as this is called code reusability.
this is the big advantage of MVC patterrn.