pg_get_notify

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

pg_get_notify — Ping 数据库连接

说明

pg_get_notify ( resource $connection , int $result_type = ? ) : array

pg_get_notify() 取得 SQL 命令 NOTIFY 发送的通告消息。要接收通告消息，必须发送 SQL 命令 LISTEN。如果连接中有通告消息，则数组包含消息名并且返回后端的 PID。如果没有消息则返回 false。

参见 pg_get_pid()。

Example #1 PostgreSQL NOTIFY 消息


<?php 
$conn = pg_pconnect("dbname=publisher");
if (!$conn) {
    echo "An error occured.\n";
    exit;
}

// Listen 'author_updated' message from other processes
pq_query($conn, 'LISTEN author_updated;');
$notify = pg_get_notify($conn);
if (!$notify)
    print("No messages\n");
else
    print_r($notify);
?>

User Contributed Notes

david at frankieandshadow dot com 22-Oct-2020 01:52


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.

glococo at gmail dot com 17-Jun-2017 08:12


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)