PHP Lambda functions

Previously, we saw how to use AWS Lambda as web hosting for complete web applications. But we can also run event-driven PHP functions on AWS Lambda.

Here is an example of a PHP Lambda function written as an anonymous function:

<?php

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

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

This form is very similar to lambdas written in other languages, for example JavaScript:

exports.myHandler = async function (event, context) {
   return "Hello " + event.name;
}

Writing functions is very useful to process events and data from other AWS services. For example, this is perfect to implement asynchronous workers, event handling, file processing, etc.

If you are looking to create HTTP applications, have a look at Bref for web apps.

The function

Functions that can run on Lambda can be an anonymous function or any kind of callable supported by PHP.

<?php

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

return function ($event) {
    return /* result */;
};

The function:

• takes an $event parameter which contains data from the event that triggered the function (list of examples here)
• can optionally return a result: the result must be serializable to JSON

There can only be one function returned per PHP file.

Context

The function is invoked with the $event parameter as well as a $context parameter. This parameter can be optionally declared if you want to use it:

<?php

use Bref\Context\Context;

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

return function ($event, Context $context) {
    return /* result */;
};

The Context object is inspired from the context parameter in other languages and provides information about the current lambda invocation (the request ID, the X-Ray trace ID, etc.).

Deployment configuration

Below is a minimal serverless.yml to deploy a function. To create it automatically, run vendor/bin/bref init.

service: app
provider:
    name: aws
    runtime: provided.al2
plugins:
    - ./vendor/bref/bref
functions:
    hello:
        handler: my-function.php
        runtime: php-81

The runtime to use is php-XX. To learn more check out the runtimes documentation.

Invocation

A PHP function must be invoked via the AWS Lambda API, either manually or by integrating with other AWS services.

If you instead want to write a classic HTTP application read Bref for web apps.

CLI

A PHP function can be triggered manually from the CLI using the serverless invoke command:

$ serverless invoke -f <function-name>
# The function name is the one in serverless.yml, in our example that would be `hello`:
$ serverless invoke -f hello
"Hello world"

To pass event data to the lambda use the --data option. For example:

serverless invoke -f <function-name> --data='{"name": "John" }'

Run serverless invoke --help to learn more about the invoke command.

From PHP applications

A PHP function can be triggered from another PHP application using the AWS PHP SDK:

You first need to install the AWS PHP SDK by running

$ composer require aws/aws-sdk-php

$lambda = new \Aws\Lambda\LambdaClient([
    'version' => 'latest',
    'region' => '<region>',
]);

$result = $lambda->invoke([
    'FunctionName' => '<function-name>',
    'InvocationType' => 'RequestResponse',
    'LogType' => 'None',
    'Payload' => json_encode(/* event data */),
]);

$result = json_decode($result->get('Payload')->getContents(), true);

A lighter alternative to the official AWS PHP SDK is the AsyncAws Lambda package.

From other AWS services

Functions are perfect to react to events emitted by other AWS services.

For example, you can write code that processes new SQS events, SNS messages, new uploaded files on S3, DynamoDb insert and update events, etc.

This can be achieve by configuring which events will trigger your function via serverless.yml. Learn more about this in the Serverless documentation.