PHP db2_pconnect- SET SCHEMA question

I am using db2_pconnect to establish a persistent connection and I change
the default schema using "SET SCHEMA" for certain queries. I generally
use a wrapper to retrieve my connection and always initialize with
the i5_lib option, but my concern is what happens if I do not? Try as I
may I have not found documentation on the behavior of db2_pconnect when it
comes to a default schema. How and when does db2_pconnect reset the
default schema? Does it always initialize the default schema for each
connection even when the i5_lib option is not provided? My concern is that
the schema change made in one session will persist to the next.

I know the library list changes stay persist, but my hope is that the
default schema is reset with each new connection/session.