Code snippet for Lambda-DynamoDB integration

[baannamr-aws]

Issue #, if available: Creating a simple PHP Lambda function example for the Lambda-DynamoDB integration.

Description of changes: Tested using the sample event from: https://docs.aws.amazon.com/lambda/latest/dg/with-ddb-example.html#with-dbb-invoke-manually

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.