我正在尝试按照本教程连接到我的aws mysql数据库：https://docs.aws.amazon.com/zh_cn/elasticbeanstalk/latest/dg/create_deploy_php.rds.html#php-rds连接。
我的代码

<?php
$dbhost = $_SERVER['RDS_HOSTNAME'];
$dbport = $_SERVER['RDS_PORT'];
$dbname = $_SERVER['RDS_DB_NAME'];
$charset = 'utf8' ;

$dsn = "mysql:host={$dbhost};port={$dbport};dbname={$dbname};charset={$charset}";
$username = $_SERVER['RDS_USERNAME'];
$password = $_SERVER['RDS_PASSWORD'];

$pdo = new PDO($dsn, $username, $password);
?>

输出

SQLSTATE[HY000] [2002] No connection could be made because the target machine actively refused it.

我可以用mysql工作台连接到我的数据库。
任何帮助都将不胜感激！