php noob question

I have a plugin that creates profiler for users. I wanted to link the profile of the user to another plugin I have. I already located the part where I have to change but I am new to php. the line is:

$link = ‘/profiles?user=#’, # here you have to be the user name and I also already know that to draw the user name I have to use:

pf_get_display_name ($ id)

just do not know the code that I have to use to call this function there.
has as someone gives me the helps ?. thx!