Same hell for me, but I can get a "slightly better error" by doing this :
$dbcnn = ocilogon("scott@database", "tiger");
rather than
$dbcnn = ocilogon("scott", "tiger", "database");
I obtain
ORA-12203: TNS:unable to connect to destination
which means that at least the tnsnames.ora file is reached.
ok, it doesn't work... but it is maybe a step forward ?