string pg_result_error_field ( resource $result , int $fieldcode )
pg_result_error_field() returns one of the detailed error message fields associated with result resource. It is only available against a PostgreSQL 7.4 or above server. The error field is specified by the fieldcode. Because pg_query() and pg_query_params() return FALSE if the query fails, you must use pg_send_query() and pg_get_result() to get the result handle. If you need to get additional error information from failed pg_query() queries, use pg_set_error_verbosity() and pg_last_error() and then parse the result.
A string containing the contents of the error field, NULL if the field does not exist or FALSE on failure.