Amazon S3 AWS上传特定目录（API / PHP）

I'm having a hard time getting the S3 upload to work. My goal is to:

• Login using credentials stored in .aws/credentials
• Gather all css files in ../css/ directory
• Upload to S3 folder with a different name such as sharedcss/

I was unable to successfully read from the .aws/credentials file, so I'm hard coding my access/secret key for now. This is my script where it stands. What am I doing wrong here?

UploadCSS.php:

<?php
require '/vendor/autoload.php';
use Aws\S3\S3Client;
use Aws\S3\Exception\S3Exception;

$buckets = array();
$css_dir = "../css/";

$client = S3Client::factory(
    array(
        'key'    => "MyAccessKeyAsAQuotedString",
        'secret' => "MySecretKeyAsAQuotedString"
    )
);

echo "Scanning $css_dir
";
$files = scandir($css_dir);

foreach ($files as $file) {
    $success = false;
    $ext = (string) end(explode('.', $file));

    if ($ext == "css") {
        $buckets[] = $file;
    }
}

foreach ($buckets as $key => $bucket) {
    echo "Uploading $bucket
";

    try {
        $result = $client->putObject(array(
            'Bucket'     => $bucket, //EDITED 
            'Key'        => "sharedcss/$bucket" ,
            'SourceFile' => "../css/$bucket"
        ));

        $client->waitUntil('ObjectExists', array(
            'Bucket' => $this->bucket,
            'Key'    => 'data_from_file.txt'
        ));
    } catch (S3Exception $e) {
        echo $e->getMessage();
    }
}

Errors:

Fatal error: Uncaught exception 'Guzzle\Common\Exception\RuntimeException' with message 'The PHP cURL extension must be installed to use Guzzle.' in /scripts/vendor/guzzle/guzzle/src/Guzzle/Http/Client.php:72
Stack trace:
#0 /scripts/vendor/aws/aws-sdk-php/src/Aws/Common/Client/AbstractClient.php(76): Guzzle\Http\Client->__construct('https://s3.amaz...', Object(Guzzle\Common\Collection))
#1 /scripts/vendor/aws/aws-sdk-php/src/Aws/Common/Client/ClientBuilder.php(247): Aws\Common\Client\AbstractClient->__construct(Object(Aws\Common\Credentials\Credentials), Object(Aws\S3\S3Signature), Object(Guzzle\Common\Collection))
#2 /scripts/vendor/aws/aws-sdk-php/src/Aws/S3/S3Client.php(211): Aws\Common\Client\ClientBuilder->build()
#3 /scripts/AmazonAWS/scripts/UploadCSS.php5(18): Aws\S3\S3Client::factory(Array)
#4 {main}
  thrown in /scripts/vendor/guzzle/guzzle/src/Guzzle/Http/Client.php on line 72

Thank you in advance!