my table is dropped in PDO

This is my PDO method i used this method to save input value to SQL After reading this pdo-prepared-statements-sufficient-to-prevent-sql-injection Since Am started learning PHP i don't know this will protect form SQL injection

CODE

<?php

$servername = "localhost";
$username = "sanoj";
$password = "123456";
$dbname = "localtest";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // prepare sql and bind parameters
    $stmt = $conn->prepare("INSERT INTO filter (firstname, lastname, email) 
    VALUES (:firstname, :lastname, :email)");
    $stmt->bindParam(':firstname', $firstname);
    $stmt->bindParam(':lastname', $lastname);
    $stmt->bindParam(':email', $email);

    // insert a row
    $firstname = filter_input(INPUT_POST, 'name', FILTER_SANITIZE_STRING, FILTER_FLAG_ENCODE_AMP);
    $lastname = filter_input(INPUT_POST, 'lname', FILTER_SANITIZE_STRING, FILTER_FLAG_ENCODE_AMP);
    $email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_STRING, FILTER_FLAG_ENCODE_AMP);
    $stmt->execute();

    echo "New records created successfully";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}
$conn = null;
?>

Can some one help me will this protect from SQL injection