too long

I am trying to develop multiple theme concept in my application. But exactly how can achieve it, i don't know?

I have done so far that created multiple CSS(style-sheet) and given option to user to select any one desirable theme among them. Where i am going to include my css, just checking that which theme selected by user. Example like below

if($user_theme_selected == 'basic')
{
      echo '<link href="/plugins/bootstrap/css/theme-basic.css" type="text/css" rel="stylesheet"></link>';
}
else if($user_theme_selected == 'premium')
{
      echo '<link href="/plugins/bootstrap/css/theme-premium.css" type="text/css" rel="stylesheet"></link>';
}
else
{
      echo '<link href="/plugins/bootstrap/css/theme-default.css" type="text/css" rel="stylesheet"></link>';
}

am i going in right way to apply multiple theme in my application?

Or anyone have better and simpler way to do it?

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