Is it legal for a foster parent to move to another state with a foster child when only the childs biological father has consented to it?

You have not stated what relation you are to the child and whether you have any legal standing or parental rights in this matter to begin with, or whether you and the child have had an ongoing relationship in the recent past. That would be important to know. If the biological father has sole legal and physical custody, then yes, he likely has the right to allow the child to relocate without your authorization. But I don't believe father does have sole custody rights. And, even if that is so, that doesn't mean you are unable to seek relief in court to maintain your continued contacts with the child, assuming you have had continued contact with the child in the recent past. If you want to renew or obtain any visitation or other rights to the child, or continue to have a relationship with the child, you should act before the child has been in New York for six (6) months, at which time Pennsylvania courts may lose jurisdiction and you may have to litigate in New York State.  As I stated above, it is unclear to me why the child is in a foster home when, as you suspect, the biological father has legal and physical rights. More likely the child has been declared dependent and an agency has legal custody rights, not the biological father.