如何解决ec2，弹性beanstalk php应用程序的连接错误问题

I have recently started working with amazons cloud specifically the elastic beanstalk and RDS components.

I have setup my EC2 SERVER

I have setup my RDS INSTANCE

I have also setup my elastic beanstalk app, a single page that needs to query a my database please see below

<?php
$servername = $_SERVER['RDS_HOSTNAME'];
$username = $_SERVER['RDS_USERNAME'];
$password = $_SERVER['RDS_PASSWORD'];
$dbname = $_SERVER['RDS_DB_NAME'];

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT * FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "Email: " . $row["Email"]. " - Name: " . $row["fname"]. " " . $row["lname"]. "<br>";
    }
} else {
    echo "0 results";
}
$conn->close();
?>

I have also been able to access my mysql database created on RDS and accessed it with work bench.

the problem I am having presently with my application hosted using beanstalk is when I try accessing my application I am getting

Connection failed: Connection timed out error

please I need help about getting this solved I am new to this whole amazon cloud thing, but its really exciting I must say.

Thanks