How do I make curve effect on background (curve background, panorama effect on background)?

I would like to making above effect on background (curve background, panorama effect on background)?

I already used Sphere effect, But the background have to reverse, so I'm trying to find other way to making this effect.

Do you have any idea to making it (please ignore Sphere effect)?

I believe that there is no curvature effect, only the background image was drawn curved so that it looks like a curvature effect. It makes the background image larger than the viewport size and gives you the possibility to move it to see more to the right and left. This game was made in the game maker, which is a 2d program, I don't think they used a sphere effect here. It's a trick, like an optical illusion. I believe ..

Thank Lancifer and lincolnsalles for your answers. Seem only Sphere effect should be use here. I will try to use it :)