pg_result_error() returns any error message associated with the result resource. Therefore, the user has a better chance of getting the correct error message than with pg_last_error().
The function pg_result_error_field() can give much greater detail on result errors than pg_result_error().
Because pg_query() returns FALSE if the query fails, you must use pg_send_query() and pg_get_result() to get the result handle.
PostgreSQL query result resource, returned by pg_query(), pg_query_params() or pg_execute() (among others).