PDO MYSQL PHP prepare（）和execute（）

its not linking up to the database. I've been trying to use prepare() and execute() to get it to post on the database but nothing shows up what am I doing wrong?

<?php
    try {
        $dbh = new PDO('mysql:host=localhost;dbname=phpexample', 'root', '');
    }
    catch (PDOException $e) 
    {
        echo "Connection error: " . $e->getMessage();
    }

    $query ="INSERT INTO products (id, sku, name) VALUES (:id, :sku, :title)";
    $stmt = $dbh->prepare($query);

    $id = NULL;
    $sku = 'MN873213';
    $title = 'Minty Mouthwash';

    //binding parameters
    $stmt->bindParam(':id', $id);
    $stmt->bindValue(':sku', $sku);
    $stmt->bindValue(':title', $title);

    //execute the query
    $stmt->execute();
?>