PHP GD: Create image reflection with gradient placed inset beneath a non-straight edge PNG

So I have a transparent image, with a curved bottom, and I would like to create a reflection.

As the image itself has a curved bottom (it's a bottle), I would like the reflection to actually start before the bottom of the transparent image, so that the reflection is partially covered by elements of the original image.

For instance in this photo, you can see that the reflection starts on the Y axis, before the object itself ends. As opposed to this image which loses the realistic effect of the reflection as there is no overlap.

I have been following a guide at TalkPHP however I'm not able to adapt it to my needs simply due to feeling a bit like I've t开发者_如何学Chrown myself in at the deep end!