Gravity form filter to handle file upload integration with WP Offload S3 Lite plugin. Adapted from https://wordpress.org/support/topic/support-for-gravity-forms-uploads.

gform_s3_uploader.php

<?php 

include_once( ABSPATH . 'wp-admin/includes/plugin.php' ); 
require_once WP_CONTENT_DIR.'/plugins/amazon-web-services/vendor/aws/aws-autoloader.php';
use \Aws\S3\S3Client;

add_filter('gform_upload_path', 'gform_change_upload_path', 10, 2);
add_action('gform_after_submission', 'gform_submit_to_s3', 10, 2);

//change gravity form upload path to point to S3
function gform_change_upload_path($path_info, $form_id)
{
	$bucket_info = get_option('tantan_wordpress_s3');
	$as3cf_is_active = is_plugin_active('amazon-s3-and-cloudfront/wordpress-s3.php');

	if(!empty($bucket_info['bucket']) && $as3cf_is_active )
	{
		$gform_link = explode('wp-content/uploads/', $path_info["url"]);
		$domain = $bucket_info['bucket'];

		if($bucket_info['domain'] == 'subdomain')
		{
			$domain = $bucket_info['bucket'].'.s3.amazonaws.com';
		}
		else if($bucket_info['domain'] == 'path')
		{
			$domain = 's3.amazonaws.com/'.$bucket_info['bucket'];
		}
		else if($bucket_info['domain'] == 'cloudfront')
		{
			$domain = $bucket_info['cloudfront'];
		}

		$protocol = ($bucket_info['ssl'] !== 'request' ? $bucket_info['ssl'] : 'http'.(!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on' ? 's' : ''));
		$path_info["url"] = (strpos($domain, 'http') === false ? $protocol : '')."://".$domain.'/'.$gform_link[1];
	}

	return $path_info;
}

//submit file to s3
function gform_submit_to_s3($entry, $form)
{
	$bucket_info = get_option('tantan_wordpress_s3');
	$as3cf_is_active = is_plugin_active('amazon-s3-and-cloudfront/wordpress-s3.php');

	if(!empty($form['fields']) && !empty($bucket_info['bucket']) && $as3cf_is_active )
	{
		$s3Client =S3Client::factory(array(
		    'key'    => AWS_ACCESS_KEY_ID, 
		    'secret' => AWS_SECRET_ACCESS_KEY
		));

		foreach ($form['fields'] as $field)
		{
			if($field->type == 'fileupload' && !empty($entry[$field->id]))
			{
				$gform_link = explode('/gravity_forms/', $entry[$field->id]);
				$upload_dir = wp_upload_dir();
				$file_url = $upload_dir['baseurl'].'/gravity_forms/'.$gform_link[1];
				$url_parts = parse_url( $file_url );
				$full_path = $_SERVER['DOCUMENT_ROOT'] . $url_parts['path'];

				$s3Client->putObject(array(
					 'Bucket'           => $bucket_info['bucket'],
					    'Key'          => 'gravity_forms/'.$gform_link[1],
					    'SourceFile'   => $full_path,
					    'ACL'          => 'public-read',
					));
			}
		}
	}
}

?>

When I use this script I am getting this error:

Fatal error: Uncaught Aws\S3\Exception\InvalidAccessKeyIdException: AWS Error Code: InvalidAccessKeyId, Status Code: 403, AWS Request ID: AEC8CF0F9A8CCFFC, AWS Error Type: client, AWS Error Message: The AWS Access Key Id you provided does not exist in our records., User-Agent: aws-sdk-php2/2.8.18 Guzzle/3.9.3 curl/7.19.7 PHP/5.4.45 thrown in /home/domain/wp-content/plugins/amazon-web-services/vendor/aws/Aws/Common/Exception/NamespaceExceptionFactory.php on line 91

I have checked and my access key ID is correct. What else could I check to fix this error?

Hi Joseph,

Please check if you have the following constants defined:

define( 'AWS_ACCESS_KEY_ID', ...); //put your access key value here
define( 'AWS_SECRET_ACCESS_KEY', ...); //put your access key here
define( 'AS3CF_BUCKET', ...); // put your bucket name

WP Offload S3 Lite needs them, normally I put it in wp-config.php

Can you try to upload using the desktop apps such as S3 Browser / Cyberduck as well? If your access and secret keys are correct then your files should be uploaded. But if you have any issue, you probably want to check your Amazon IAM manager, find your user with the specified key and attach policy to allow it to access S3 resources.

Sorry, but where do I put this file? Can I put all logic in functions.php?