We're looking for scaling a PHP application. Googling around take us to find out that AWS Lambda is the most scalable service out there.
Not only that, we also have https://serverless-visually-explained.com/ which walk us through what we need to know to get PHP up and running on AWS Lambda.
If this is a deal-breaker for your application, a workaround could be to use Application Load Balancer instead.
If your project uses too many exotic PHP extensions, you may end up hitting the limit of 5 layers per function.