index.php

<?php declare(strict_types=1);

require __DIR__.'/vendor/autoload.php';

lambda(function (array $event) {
    return 'Hello ' . ($event['name'] ?? 'world');
});

serverless.yml

service: app

provider:
    name: aws
    region: us-east-1
    runtime: provided

plugins:
    - ./vendor/bref/bref

functions:
    website:
        handler: index.php
        description: ''
        layers:
            - ${bref:layer.php-73-fpm}
        events:
            -   http: 'ANY /'
            -   http: 'ANY /{proxy+}'