If odbc_fetch_row() was succesful (there was a row), TRUE is returned. If there are no more rows, FALSE is returned.
If row_number is not specified, odbc_fetch_row() will try to fetch the next row in the result set. Calls to odbc_fetch_row() with and without row_number can be mixed.
To step through the result more than once, you can call odbc_fetch_row() with row_number 1, and then continue doing odbc_fetch_row() without row_number to review the result. If a driver doesn't support fetching rows by number, the row_number parameter is ignored.