Amazon S3 pre-signed POSTs with Amazon SDK for PHP Version 3 - Amazon SDK for PHP
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Amazon S3 pre-signed POSTs with Amazon SDK for PHP Version 3

Much like pre-signed URLs, pre-signed POSTs enable you to give write access to a user without giving them Amazon credentials. Pre-signed POST forms can be created with the help of an instance of AwsS3PostObjectV4.

The following examples show how to:

  • Get data for an S3 Object POST upload form using PostObjectV4.

All the example code for the Amazon SDK for PHP is available here on GitHub.



PostObjectV4 does not work with credentials sourced from Amazon IAM Identity Center.

Before running the example code, configure your Amazon credentials, as described in Credentials. Then import the Amazon SDK for PHP, as described in Basic usage.

Create PostObjectV4

To create an instance of PostObjectV4, you must provide the following:

  • instance of Aws\S3\S3Client

  • bucket

  • associative array of form input fields

  • array of policy conditions (see Policy Construction in the Amazon Simple Storage Service User Guide)

  • expiration time string for the policy (optional, one hour by default).


require '../vendor/autoload.php'; use Aws\S3\PostObjectV4; use Aws\S3\S3Client;

Sample Code

require '../vendor/autoload.php'; use Aws\S3\PostObjectV4; use Aws\S3\S3Client; $client = new S3Client([ 'profile' => 'default', 'region' => 'us-east-1', ]); $bucket = 'doc-example-bucket10'; $starts_with = 'user/eric/'; $client->listBuckets(); // Set defaults for form input fields. $formInputs = ['acl' => 'public-read']; // Construct an array of conditions for policy. $options = [ ['acl' => 'public-read'], ['bucket' => $bucket], ['starts-with', '$key', $starts_with], ]; // Set an expiration time (optional). $expires = '+2 hours'; $postObject = new PostObjectV4( $client, $bucket, $formInputs, $options, $expires ); // Get attributes for the HTML form, for example, action, method, enctype. $formAttributes = $postObject->getFormAttributes(); // Get attributes for the HTML form values. $formInputs = $postObject->getFormInputs(); ?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <title>PHP</title> </head> <body> <form action="<?php echo $formAttributes['action'] ?>" method="<?php echo $formAttributes['method'] ?>" enctype="<?php echo $formAttributes['enctype'] ?>"> <label id="key"> <input hidden type="text" name="key" value="<?php echo $starts_with ?><?php echo $formInputs['key'] ?>"/> </label> <h3>$formInputs:</h3> acl: <label id="acl"> <input readonly type="text" name="acl" value="<?php echo $formInputs['acl'] ?>"/> </label><br/> X-Amz-Credential: <label id="credential"> <input readonly type="text" name="X-Amz-Credential" value="<?php echo $formInputs['X-Amz-Credential'] ?>"/> </label><br/> X-Amz-Algorithm: <label id="algorithm"> <input readonly type="text" name="X-Amz-Algorithm" value="<?php echo $formInputs['X-Amz-Algorithm'] ?>"/> </label><br/> X-Amz-Date: <label id="date"> <input readonly type="text" name="X-Amz-Date" value="<?php echo $formInputs['X-Amz-Date'] ?>"/> </label><br/><br/><br/> Policy: <label id="policy"> <input readonly type="text" name="Policy" value="<?php echo $formInputs['Policy'] ?>"/> </label><br/> X-Amz-Signature: <label id="signature"> <input readonly type="text" name="X-Amz-Signature" value="<?php echo $formInputs['X-Amz-Signature'] ?>"/> </label><br/><br/> <h3>Choose file:</h3> <input type="file" name="file"/> <br/><br/> <h3>Upload file:</h3> <input type="submit" name="submit" value="Upload to Amazon S3"/> </form> </body> </html>