How Can I merge char variable

To resume,
I have this

gps.getPar(lon,lat,alt,time,vel);

and it should be in the coords variable of this

inet.httpPOST(host, port_post, path_post, coords , "Result", 1000);

But I hav to add URL varaiable like this

coords = "lat="+lat+"&long="+lon+"&alt="+alt+"&speed=&course="+val+"&date=2013-04-25&time="+time+";