What is the phantom in the conclusion of the Diamond Sutra? This is the version I am referring to:


  Thus shall ye think of this fleeting world: A star at dawn, a bubble
  in a stream; A flash of lightning in a summer cloud; A flickering
  lamp, a phantom, and a dream.
No phantom, no...



The Diamond Sutra in Classical Chinese, wherein one of the verses instantly enlightened the 6th Patriarch Huineng, the corresponding verse to your quote is this: 


  一切有為法，如夢幻泡影，如露亦如電，應作如是觀。


This beautiful verse was done by this guy with his league of national selected translators:

 

Kumarajiva is held by some Great Buddhist Masters as the "return of Sariputra". A memorial was built for him right after his cremation wherein housed his tongue Śarīra,  Kumarajiva Temple in Gangsu, China:



Recently out of curiosity I studied some Vinayas, one incident got description of Sariputra, said he was with small built; immediately echoing with the above image in my mind... though that saying remained just a saying. 



If I render the above verse, it should read as:

All conditional things are, like mirages of the bubbles also an illusive dream, like dews also as if lightning, as such thus should be seen.

This verse transmitting the message that all existences are empty, constructed as if mirages and dreams; short-lived like morning dews, fleeting like lightning.

The phantom could be a different translation of mirage. A star at dawn could be the different translation of dew since by sunrise the dew will evaporate without trace... etc.