[PHP] attach an ICO file to a text file...then downloading to the user

[grahama]

is it possible to add a custom icon to a text file on the server 
side......and then download the completed file to the user's desktop

would you put some type of AddType into the htacccess folder to do this 
?
like  AddType image/x-icon .ico

can php do something like this ?
many thanks
g