Snippet to add attachments to a salesforce object that is created through the salesforce plugin for gravityforms by @katzwebservices

wp_salesforce_add_attachments.php

add_action("gform_after_submission", 'sf_add_attachments', 11, 2);

/**
 * This will go through all your fileupload fields from the form, 
 * and it will create an attachment for each one of the that is not empty
 * @param  [type] $entry [description]
 * @param  [type] $form  [description]
 */
function sf_add_attachments($entry, $form){
    $parentID = gform_get_meta($entry['id'], 'salesforce_id');
    if($parentID){
        $base_dir = wp_upload_dir();
        $base_dir = $base_dir['basedir'];

        $fields = GFCommon::get_fields_by_type($form, array("fileupload"));
        $attachments = array();
        foreach ($fields as &$field) {
            if(!empty($entry[$field['id']])){
                $filepath = $entry[$field['id']];
                $filepath = $base_dir.substr($filepath, strpos($filepath, 'uploads')+7); 
                $filename = pathinfo($filepath, PATHINFO_BASENAME);

                $handle = fopen($filepath,'rb');
                $file_content = fread($handle, filesize($filepath));
                fclose($handle);
                $encoded = chunk_split(base64_encode($file_content));

                $attachment_fields = array('Name' => $filename,
                            'ParentId' => $parentID);

                $attachment_fields = array_map(array('GFSalesforce', '_convert_to_utf_8'), $attachment_fields);

                $attachment_fields['body'] = $encoded;

                $sObject = new stdClass();
                $sObject->type = 'Attachment';
                $sObject->fields = $attachment_fields;

                $attachments[] = $sObject;
            }
        }
        
        $api = GFSalesforce::get_api();
        $results = $api->create($attachments);
        
        foreach ($results as $result) {
            if($result->success){
                RGFormsModel::add_note($entry['id'], 0, __('Gravity Forms PoP Custom Integration'), sprintf('An attachment with Id #%s has been added on salesforce for this object', $result->id));
            }else{
                RGFormsModel::add_note($entry['id'], 0, __('Gravity Forms PoP Custom Integration'), sprintf('An error occurred Error: %s', $result->errors[0]->message));
            }
        }

    }

}