OCIPLogon() creates a persistent
connection to an Oracle 8 database and logs on. The optional
third parameter can either contain the name of the local
Oracle instance or the name of the entry in tnsnames.ora to
which you want to connect. If the optional third parameter is
not specified, PHP uses the environment variables ORACLE_SID
(Oracle instance) or TWO_TASK (tnsnames.ora) to determine
which database to connect to.
See also OCILogon() and
OCINLogon().