PhP在选定值的情况下添加天/月

Ok I will try to be explicit, I made a script with a form, I need to introduce some informations like name telephone and here is the interesting thing: Start Date, Number of Months ( In my case 1 month, 6 months and 12 months ) and end date. I complete the start date with jquery_ui timp stamp and I select my option for how many months and I want to make the End Date like this = Start_Date + x months and store them into my database. ` Data inceperii asigurarii: Ok I will try to be explicit, I made a script w