Can a prepositional phrase act as an indirect object?

Solution 1:

Yes, a benefactive such as "for my mum" behaves like an indirect object, in that it can often appear before the direct object without the preposition:

I baked my mum a cake.

She sewed me a shirt.

But this is not natural for all verbs, and I'm not sure what rule will predict it. So

? He dug me the garden.

does not sound right to me whereas "He dug the garden for me" is fine.

I think the availability of this construction depends on whether the actor ends up providing an object rather than just a service to the beneficient, but I'm not sure. Consider

She painted me a picture.

which is fine, but

? She painted me the house.

which sounds odd to my ear.