Php fatal error - call to a member function prepare() on resource

<?php include 'connectionDetails.php'; ?>

<?php


if (isset($_POST['noteid1'], $_POST['notetext1'])) 
{
    var_dump($_POST['notetext1']);

    $stmt = $conn->prepare("UPDATE Notes SET Note = ? WHERE NoteID = ?");
    $stmt->bind_param("si", $notetext2, $noteid2);

    $noteid2 = $_POST['noteid1'];
    $notetext2 = $_POST['notetext1'];
    $stmt->execute();

    $stmt->close();
}
else
{
    if (isset($_POST['notetext1'])) {
        var_dump($notetext2);
    }
    else
    {
        echo "Test";
    }

}


?>
connectionDetails.php:

<?php
$myServer = "test ip";
$connectionInfo = array('Database' => 'DiscoverThePlanet', 'UID' => 'Test', 'PWD' => 'Test');

//connection to the database
$conn = sqlsrv_connect($myServer, $connectionInfo)
  or die("Couldn't connect to SQL Server on $myServer"); 

//Test connection to server
// if ($conn) 
// {
//     echo "connection successful";    # code...
// }

?>
///The error is in the submitNoteText.php and is this line://

$stmt = $conn->prepare("UPDATE Notes SET Note = ? WHERE NoteID = ?");