A PHP is a six-hour-a-day treatment program usually based at a hospital or a clinic that treats OCD.
Typically there will be some group work and some individual exposure work specifically focused on the OCD. There may also be other treatment formats, such as art therapy groups, spirituality groups, medication management groups, and other groups focused on depression, codependency, and so on.
All of these groups meet over the course of six hours a day, five days a week (depending on how your state and insurance carriers define PHP treatment, it may be a bit different in your area), and then the patient returns home for the night. In PHP, a patient also has access to a psychiatrist for medication consultations.
The goal of a PHP is, of course, to specifically address the OCD difficulties and other troubles, such as depression, that may be related to OCD. The treatment team consists of numerous professionals, such as psychologists, psychiatrists, nurses, and therapists.
PHP is used either to assist people as they step down from inpatient care and slowly reenter their everyday lives or to give people who have not needed inpatient care but do require a significant amount of therapy a chance to get the help they need.