pg_send_query() send
asynchronous query to the
connection. Unlike
pg_query(), it can send multiple
query to PostgreSQL and get the result one by one using
pg_get_result(). Script execution is not blocked
while query is executing. Use
pg_connection_busy() to check connection is busy
(i.e. query is executing). Query may be canceled by calling
pg_cancel_query().
Although user can send multiple query at once, user
cannot send multiple query over busy connection. If query is
sent while connection is busy, it waits until last query is
finished and discards all result.
See also pg_query(),
pg_cancel_query(),
pg_get_result() and
pg_connection_busy()