Valid options are PGSQL_DML_NO_CONV, PGSQL_DML_EXEC, PGSQL_DMP_ASYNC, PGSQL_DML_STRING (pulled out of source code).
This function does not support selecting from multiple tables. You can get around this by setting the PGSQL_DML_NO_CONV option. This prevents the error which occurs when the function tries to convert the condition array.
I think it is also important to point out that the table_name field is not safe, particularily with the PGSQL_DML_NO_CONV option.
The arguements array field is compulsory, as documented. What isn't so clear is that the array has to actually have some values in it, you can't do a select all.
In summary, this function is good for a very small subset of basic queries. If you are after anything more complex you are better off with pg_query.