Instant yet Simple PHP notification with HTML5 Server-Sent Events
sse.php
<?php
$dbconn = new PDO("pgsql:host=localhost;dbname=mydb", "pduser", "userpass");
$dbconn->exec('LISTEN "channel_name"'); // those doublequotes are very important
header("X-Accel-Buffering: no"); // disable ngnix webServer buffering
header("Content-Type: text/event-stream");
header("Cache-Control: no-cache");
ob_end_flush(); // close PHP output buffering
$inc=0;
while (1) {
$result = "";
// wait for one Notify 10seconds instead of using sleep(10)
$result = $dbconn->pgsqlGetNotify(PDO::FETCH_ASSOC, 10000);
if ( $result ) {
echo "id: $inc\ndata: ".stripslashes(json_encode($result))."\n\n";
$inc++;
}
flush();
}
?>
Tested with HTML+JS sample file from Mozilla web site (ssedemo.php)
pg_get_notify
(PHP 4 >= 4.3.0, PHP 5, PHP 7)
pg_get_notify — Gets SQL NOTIFY message
Descrierea
pg_get_notify
( resource
$connection
, int $result_type = ?
) : array
pg_get_notify() gets notifications generated by a
NOTIFY SQL command. To receive notifications,
the LISTEN SQL command must be
issued.
Parametri
-
connection -
PostgreSQL database connection resource.
-
result_type -
An optional parameter that controls how the returned array is indexed.
result_typeis a constant and can take the following values:PGSQL_ASSOC,PGSQL_NUMandPGSQL_BOTH. UsingPGSQL_NUM, pg_get_notify() will return an array with numerical indices, usingPGSQL_ASSOCit will return only associative indices whilePGSQL_BOTH, the default, will return both numerical and associative indices.
Valorile întoarse
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.
Exemple
Example #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);
}
?>
add a note
User Contributed Notes 2 notes
glococo at gmail dot com ¶
7 years ago
david at frankieandshadow dot com ¶
4 years ago
It appears that pg_get_notify does not distinguish between no message waiting and a failure when checking - both seem to return FALSE.
I had to add a pg_check_connection(...) before pg_get_notify to check the connection is still alive (it's quite likely to be a long-standing connection with pg_get_notify as you'll be polling waiting for something to happen). In my case the remote database server had a hiccup, and without pg_check_connection the listeners failed to notice, so never saw later notifications.
