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pg_get_notify

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

pg_get_notify — 获取 SQL NOTIFY 消息

说明

pg_get_notify(PgSql\Connection $connection, int $mode = PGSQL_ASSOC): array|false

pg_get_notify() 取得 SQL 命令 NOTIFY 生成的消息。要接收通知，必须发送 SQL 命令 LISTEN。

参数

connection: PgSql\Connection 实例。
mode: An optional parameter that controls how the returned array is indexed. mode is a constant and can take the following values: PGSQL_ASSOC, PGSQL_NUM and PGSQL_BOTH. Using PGSQL_NUM, the function will return an array with numerical indices, using PGSQL_ASSOC it will return only associative indices while PGSQL_BOTH will return both numerical and associative indices.

返回值

包含 NOTIFY 消息名称和后端 PID 的 array。如果服务器支持，该数组还包含服务器版本和有效负载。否则，如果没有 NOTIFY 正在等待，则返回 false。

更新日志

版本	说明
8.1.0	现在 `connection` 参数接受 PgSql\Connection 实例，之前接受 resource。

示例

示例 #1 PostgreSQL NOTIFY 消息

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

// 从其它进程监听 'author_updated' 消息
pg_query($conn, 'LISTEN author_updated;');
$notify = pg_get_notify($conn);
if (!$notify) {
  echo "No messages\n";
} else {
  print_r($notify);
}
?>

参见

pg_get_pid() - 获取后端的进程 ID

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User Contributed Notes 2 notes

down

glococo at gmail dot com ¶

6 years ago

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)

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david at frankieandshadow dot com ¶

3 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.

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