Listening to notifications in PostgreSQL

Notification.hs

{-# LANGUAGE OverloadedStrings, RecordWildCards #-}
module Main where

import Control.Monad (forever)
import Data.ByteString.Char8 (pack)
import Database.PostgreSQL.Simple
import Database.PostgreSQL.Simple.Notification
import System.Environment (getArgs)

main = do
  [connString] <- getArgs
  conn <- connectPostgreSQL $ pack connString
  execute_ conn "LISTEN change"
  forever $ do
    Notification{..} <- getNotification conn
    print notificationPid
    print notificationChannel
    print notificationData

notification.php

<?php
$conn = pg_connect("dbname=my_database");
pg_query($conn, 'LISTEN change;');

while (true) {
  // Unfortunately PHP < 5.6 doesn't support synchronous waiting so we
  // must poll it once per second.
  $notify = pg_get_notify($conn);
  if ($notify) break;
  sleep(1);
}
print_r($notify);
?>

trigger.sql

CREATE OR REPLACE FUNCTION change_notify() RETURNS trigger AS $$ BEGIN EXECUTE 'NOTIFY change,''' || TG_TABLE_NAME || '-' || TG_OP || ''''; RETURN new; END; $$ LANGUAGE plpgsql;

CREATE TRIGGER change_trigger AFTER insert or update or delete or truncate on testi execute procedure change_notify();