The main difference between Partial Hospitalization Program (PHP), Intensive Outpatient Program (IOP), and outpatient services is the amount of time your child spends in treatment. At the PHP day program level, adolescents attend all-day programming, five days a week. The IOP level is usually five afternoons a week, following the client’s attendance at their home school. Outpatient services refer to the lowest level of teen outpatient treatment, with programming provided fewer than five afternoons a week, depending on the client’s and family’s needs and goals.