Using AWS PHP SDK on Elastic Beanstalk

Question

So I have a PHP web app on Elastic Beanstalk, and I'm trying to use the PHP AWS SDK to work with files on S3. So far I haven't got it working.  
Per this documentation:     
I have the following in a composer.json file at the root level of my application:  
{  
    "require": {  
        "aws/aws-sdk-php": "3.*"  
    }  
}  
Do I need something else in it? Like an autoload section or something?  
  
Since the aws.phar file is over 16MB, I don't want to include it in my app and have to upload it every time I make an unrelated update; from what I understand, Elastic Beanstalk already has Composer installed, and the above json should install the AWS PHP SDK on deployment.  
  
I'm thinking I need a require('/vendor/autoload.php'); or something in my code? If so, how do I know where the autoload.php file is on Elastic Beanstalk? Or do I need to create one? (And if so, what do I put in it?) When I used that line, I just get an error saying it can't find the file.  
  
I don't have a vendor folder in my application.

Answer

For future reference, I figured this out as follows.  
I had been getting "No composer.json file detected" in my logs.  
  
I discovered that because of the way I was zipping my package on macOS (using the native right click > Compress), it puts the files in a sub-folder inside the zipped package. So the composer.json was not at the "root" level of my package. I added it to the "root" level, and then once deployed I got the following in the logs:  
Found composer.json file. Attempting to install vendors. (...)  
  
And then the path to "vendor/autoload.php" was not in the directory with my application either (NOT /var/app/current/application-files/web/vendor), but closer to the root level (e.g. /var/app/current/vendor)  
  
Hopefully this saves someone else some headaches!

Using AWS PHP SDK on Elastic Beanstalk

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