Salesforce PHP API Attachment Upload

I am trying to upload an attachment using the following function.

     public function uploadAttachment($attachmentBody, $attachmentBodyLength, $attachmentName) {
    $createFields = array(
        'Body' => utf8_encode($attachmentBody),

    //    'ContentType' => $contentType,
        'Name' => $attachmentName,
        'IsPrivate' => 'false',
    );
    $sObject = new stdclass();
    $sObject->fields = $createFields;
    $sObject->type = 'Attachment';
    $sObject->body = utf8_encode ( $attachmentBody);

    echo "Creating Attachment";
    $upsertResponse = $this->SFConnection->create(array($sObject));
    print_r($upsertResponse);
}

I know that I am not currently specifying a ParentID - this is not my problem

I am getting an error "Caught exception: The element type "Body" must be terminated by the matching end-tag "" when I utf8_encode($attachmentBody). If I remove the utf8_encode I get the infamous "Invalid byte 1 of 1-byte UTF-8 sequence." problem!

Where am I going wrong? Has anyone else successfully uploaded attachments through the PHP API?