oci_free_statement doesn't always free up cursors.  I had a query where I performed the following functions in a loop:
OCIParse
OCIExecute
Oci_fetch_assoc
(Grab some field values)
OciFreeStatement
I didn't specify the use of a cursor, but ran into a "maximum 
open cursors exceeded" error.  Within my code, I had one "select * from table_with_lobs" query.  When I changed the query to be "select a, b, c, from table_with_lobs" (where I specified the actual column names and where those columns were not LOB fields) the error message went away and I didn't have to resort to upping the max_open_cursors value in Oracle.