mysql：Cpanel数据库连接php_network_getaddresses错误

Question

我在使用以下代码的Cpanel托管中面临数据库连接错误;

<?php
$servername = "localhost";
$username = "helloDB";
$password = "MY_PASS";

$conn = mysqli_connect($servername, $username, $password);

if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>

错误记录...

Connection failed: SQLSTATE[HY000] [2002] php_network_getaddresses: 
getaddrinfo failed: Name or service not known