pg_fetch_assoc() returns an associative array that
corresponds to the fetched row (records).
pg_fetch_assoc() is equivalent to calling
pg_fetch_array() with PGSQL_ASSOC as the
optional third parameter. It only returns an associative array.
If you need the numeric indices, use
pg_fetch_row().
Note: This function sets NULL fields to
the PHP NULL value.
pg_fetch_assoc() is NOT significantly
slower than using pg_fetch_row(), and
is significantly easier to use.