CompilerPass.php

<?php
declare(strict_types=1);

namespace App\Util\Logger;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Definition;
use Symfony\Component\DependencyInjection\Reference;

final class CompilerPass implements CompilerPassInterface
{
    public function process(ContainerBuilder $container)
    {
        $container->setDefinition(
            ExactOnlineLogger::class,
            new Definition(DecoratedLogger::class, [new Reference('monolog.logger.exactonline')])
        );

        $container->setDefinition(
            MailChimpLogger::class,
            new Definition(DecoratedLogger::class, [new Reference('monolog.logger.mailchimp')])
        );
    }
}

DecoratedLogger.php

<?php
declare(strict_types=1);

namespace App\Util\Logger;

use Psr\Log\LoggerInterface;

final class DecoratedLogger implements LoggerInterface, ExactOnlineLogger, MailChimpLogger
{
    /**
     * @var LoggerInterface
     */
    private $decorated;

    public function __construct(LoggerInterface $decorated)
    {
        $this->decorated = $decorated;
    }

    public function emergency($message, array $context = []): void
    {
        $this->decorated->emergency($message, $context);
    }

    public function alert($message, array $context = []): void
    {
        $this->decorated->alert($message, $context);
    }

    public function critical($message, array $context = []): void
    {
        $this->decorated->critical($message, $context);
    }

    public function error($message, array $context = []): void
    {
        $this->decorated->error($message, $context);
    }

    public function warning($message, array $context = []): void
    {
        $this->decorated->warning($message, $context);
    }

    public function notice($message, array $context = []): void
    {
        $this->decorated->notice($message, $context);
    }

    public function info($message, array $context = []): void
    {
        $this->decorated->info($message, $context);
    }

    public function debug($message, array $context = []): void
    {
        $this->decorated->debug($message, $context);
    }

    public function log($level, $message, array $context = []): void
    {
        $this->decorated->log($level, $message, $context);
    }
}

ExactOnlineLogger.php

<?php
declare(strict_types=1);

namespace App\Util\Logger;

use Psr\Log\LoggerInterface;

interface ExactOnlineLogger extends LoggerInterface
{

}

MailChimpLogger.php

<?php
declare(strict_types=1);

namespace App\Util\Logger;

use Psr\Log\LoggerInterface;

interface MailChimpLogger extends LoggerInterface
{

}