Smartphone detection

hi,

i disable a block in the config. Then i go to the page, the block is loading and for 1 second you can see it , after this it's disappear.
is there a other way? PHP , because i dont won't load content , that i didnt need for my smartphone,tablet...

is there a php if for only smartphone, or for only tablets or for only desktop?

with css it's possible: hidden-phone, hidden-desktop (not the best way)

thx