In Rails, beware that url_for has slightly different default behavior depending on whether you call it from a template or a controller. When url_for is called in a template (ActionView or Helper):
  • urls are escaped by default (ampersands become &)
  • returns relative path by default, unless a host is specified

> url_for( { :controller =>  "test",
             :action => "me",
             :foo => 1, 
             :bar => 2 } )
/test/me?foo=1&bar=2

When url_for is called in a controller (ActionController):
  • urls are not escaped by default
  • full path is returned unless only_path is specified

> url_for( { :controller =>  "test",
             :action => "me",
             :foo => 1, 
             :bar => 2 } )
http://example.com/test/me?foo=1&bar=2

There are times in a view when you want the unescaped version (such as putting into a Javascript variable, or generating a plain text file).  Simply pass escape => false:

> url_for( { :controller =>  "test",
             :action => "me",
             :foo => 1, 
             :bar => 2,
             :escape => false } )
http://example.com/test/me?foo=1&bar=2