Have user id as part of file name

Hello,

I am thinking about doing something similar to mybb attach file on the forum that I am creating codeigniter project

I notice mybb when uploads file it addeds user id plus a hash

post_1_1486872235_add64c460cbbc24fb1c9e333418ee1d4.attach

is it safe to add user ids as part of image filename?

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!