pg_field_type() returns a string containing the base type name of the given field_number in the given PostgreSQL result resource.
Note: If the field uses a PostgreSQL domain (rather than a basic type), it is the name of the domain's underlying type that is returned, rather than the name of the domain itself.
Note: This function used to be called pg_fieldtype().
PostgreSQL query result resource, returned by pg_query(), pg_query_params() or pg_execute() (among others).
Field number, starting from 0.