从今天起X天后计算

i am develop a webpage in that i need to calculate x days from a specified date , The problem is we exclude the saturday and sunday . For example $Shipdate = '06/30/2009' and the x is 5 means , i want the answer '7' [ie 30 is tuesday so after 5 days it will be sunday , so there is two holiday(saturday and sunday) so we add 5+2(for saturday and sunday)]=7. Please help me to find out , Thanks in advance.i am develop a webpage in that i need to calcul