What attaches to a camera lens to split light?

My photography showed us a picture he took and it was of Albert bridge with the lights on in the night time and the lights were split (had 4 lines coming from them) and he said he attached, what i thing he said was a light splitter on ti his, lens but i can't find one. Is there such thing and what is it actually called?
this is an example but this one looks fake

Star filter.

A star filter is only part of the answer. You can get various degrees of this filter. In the photo example shown, that is what is called an 8 point filter. Note, there are 8 spikes radiating out from each light. You can also get star filters with 4 points, or 6 points, depending on how strong you want the effect.

So when you go shopping for a star filter, you will now know what it means when it says 4pt. Or 8pt.

For consistent reliable results you need a "star filter." In the link you provided an 8-point star filter was used. In your description, a 4-point star filter is needed. The quality of your star filter will obviously affect your end outcome, some cheaper star filters will add give the image a very soft feel to it, wheras etched glass filters perform much better.

You'll also find that this effect can be created without. A lot of modern lenses naturally do this with an intense but small light source, like here: and The 17-40mm f4L does it rather readily.