For example, in the sentence: I baked a cake for my mom. 

Direct object (DO): cake
Indirect object (IO): for my mom

Some webpages say [IO can only come before DO](http://www.softschools.com/examples/grammar/indirect_object_examples/77/) 

While others explain that [a prepositional phrase can also act as IO](http://www.chompchomp.com/terms/indirectobject.htm) 

Can a prepositional phrase act as an indirect object?