Example of how to extend Lumen monolog implementation for New Relic and potentially other handlers

Myapp.php

<?php namespace Foo;

// app/Myapp.php
use Monolog\Logger;
use Laravel\Lumen\Application;
use Monolog\Handler\StreamHandler;
use Monolog\Formatter\LineFormatter;
use Monolog\Handler\NewRelicHandler;

class Myapp extends Application
{
    /**
     * This replaces the inline array used in \Lumen\Application to allow multiple handlers
     *
     * @return void
     */
    protected function registerLogBindings()
    {
        $this->singleton('Psr\Log\LoggerInterface', function () {
            return new Logger('lumen', $this->getMonologHandler());
        });
    }


    /**
     * Extends the default logging implementation with additional handlers if configured in .env
     *
     * @return array of type \Monolog\Handler\AbstractHandler
     */
    protected function getMonologHandler()
    {
        $handlers = [];

        $handlers[] = (new StreamHandler(storage_path('logs/lumen.log'), Logger::DEBUG))->setFormatter(new LineFormatter(null, null, true, true));

        if (extension_loaded('newrelic')) {
            // configure New Relic monolog Handler
            newrelic_set_appname(env('APP_NAME', 'Hodor v2'));

            $handlers[] = new NewRelicHandler(Logger::ERROR, true);
        }

        return $handlers;
    }
}

start.php

<?php 
// bootstrap/start.php
....

$app = new \Foo\Myapp(
    realpath(__DIR__.'/../')
);

...