/xC3/xA1

In php, "C!" must be used "/xC3/xA1"to stand for. For example,
$output="/xC3/xA1", then in the display it is "C!". However, if i
wrote a code function convertUnicode to convert a character   to be
that:   $output="\x".sprintf("%x",$input); Even the $output =/xC3/xA1,
the display is xC3/xA1, not C!. I don't know why, can someone help me
on this? Or is there other way to stand for C!, I mean for example in
decimal? I know it is 195 161. But I don't know how to write it?


Thanks

Helen