(PHP 4 >= 4.3.0, PHP 5, PHP 7)
pg_get_notify — Gets SQL NOTIFY message
$connection
   [, int $result_type
  ] ) : arraypg_get_notify() gets notifications generated by a NOTIFY SQL command. To receive notifications, the LISTEN SQL command must be issued.
connectionPostgreSQL database connection resource.
result_type
       An optional parameter that controls
       how the returned array is indexed.
       result_type is a constant and can take the
       following values: PGSQL_ASSOC, 
       PGSQL_NUM and PGSQL_BOTH.
       Using PGSQL_NUM, pg_get_notify()
       will return an array with numerical indices, using
       PGSQL_ASSOC it will return only associative indices
       while PGSQL_BOTH, the default, will return both
       numerical and associative indices.
      
   An array containing the NOTIFY message name and backend PID.
   As of PHP 5.4.0 and if supported by the server, the array also contains the server version and the payload.
   Otherwise if no NOTIFY is waiting, then FALSE is returned.
  
Ejemplo #1 PostgreSQL NOTIFY message
<?php 
$conn = pg_pconnect("dbname=publisher");
if (!$conn) {
  echo "An error occurred.\n";
  exit;
}
// Listen 'author_updated' message from other processes
pg_query($conn, 'LISTEN author_updated;');
$notify = pg_get_notify($conn);
if (!$notify) {
  echo "No messages\n";
} else {
  print_r($notify);
}
?>