$host = "myinstance.c8rse3unpyyi.ap-northeast-2.rds.amazonaws.com";
$user = "myUsername";
$pass = "myPW";
$dbname = "testDB";
$conn = mysqli_connect($host, $user, $pass, $dbname, 3306);

if ($conn) {
    echo "connect_success";
} else {
        echo "connect_fail";
}

# select
$sql = "INSERT INTO test (NAME, NUM)
        VALUES ('john', '3')";
if (mysql_query($sql)) {
    echo "query_sended!";
} else {
    echo "query_failed..";
};