By just adjusting blur on a surface in photoshop, you get a subject that is sharp, the rest blurred... but in most 3D perspectives, a lot of things return from the background back to the foreground. So the trick won't work perfectly in photoshop.
Besides, the blur needs to get gradually heavier in distance on your image, that is called the depth of field. And no photoshop can know in advance which field is further away from the lens.
Even if you don't know how to set a higher aperture (rtfm), you can always set your camera to an automatic 'portrait/macro' mode.