从PHP查询表（配置文件？）

I am trying to create a few php pages for my website. Basically, I want to query a table for a database thats connected with my website and be able to store/retrieve information from this table.

I have purchased a hosting service and to the best of my knowledge have correctly set up a database on phpMyAdmin. I have also set up a username and password for access (so DATABASE NAME, SERVER, USERNAME, PASSWORD).

However, I am using the following function to query from my table.

function query(/* $sql [, ... ] */)
{
    // SQL statement
    $sql = func_get_arg(0);

    // parameters, if any
    $parameters = array_slice(func_get_args(), 1);

    // try to connect to database
    static $handle;
    if (!isset($handle))
    {
        try
        {
            // connect to database
            $handle = new PDO("mysql:dbname=" . DATABASE . ";host=" . SERVER, USERNAME, PASSWORD);

            // ensure that PDO::prepare returns false when passed invalid SQL
            $handle->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); 
        }
        catch (Exception $e)
        {
            // trigger (big, orange) error
            trigger_error($e->getMessage(), E_USER_ERROR);
            exit;
        }
    }

    // prepare SQL statement
    $statement = $handle->prepare($sql);
    if ($statement === false)
    {
        // trigger (big, orange) error
        trigger_error($handle->errorInfo()[2], E_USER_ERROR);
        exit;
    }

    // execute SQL statement
    $results = $statement->execute($parameters);

    // return result set's rows, if any
    if ($results !== false)
    {
        return $statement->fetchAll(PDO::FETCH_ASSOC);
    }
    else
    {
        return false;
    }
}

When I try something simple like query("Select * From table"), I get the following error message

Fatal error: SQLSTATE[HY000] [1045] Access denied for user 'user'@'localhost' (using password: YES) in /home/user/includes/functions.php on line 142

Please, any help would be greatly appreciated. I looked online and it looks like some forums have mentioned that I need to check my config file as per the advice of this post: https://forums.cpanel.net/threads/error-link-to-database-cannot-be-established.394212/

Edit: I do not have mySQL on my computer. I am using a windows. I set up the database inside of phpMyAdmin in cpanel.

Something like this:

$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $handle->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 results";
}
$handle->close();

Please see the section Granting user permissions part of https://www.digitalocean.com/community/tutorials/how-to-create-a-new-user-and-grant-permissions-in-mysql