emails/api/setup/app.php

<?php
use DI\ContainerBuilder;
use DI\Bridge\Slim\Bridge;

require_once 'composer.php';

$builder = new ContainerBuilder();

$folders = [
    'settings',
    'setups'
];

foreach ($folders as $f) {
    $folder = implode(DIRECTORY_SEPARATOR, [
        __DIR__,
        $f
    ]);
    if (!file_exists($folder)) {
        continue;
    }
    $files = new FilesystemIterator($folder);
    foreach ($files as $file) {
        if ($file->isDir()) {
            continue;
        }
        $builder->addDefinitions($file->getRealPath());
    }
}
$app = Bridge::create($builder->build());

$folder = implode(DIRECTORY_SEPARATOR, [
    __DIR__,
    'middleware'
]);
if (file_exists($folder)) {
    $files = new FilesystemIterator($folder);
    foreach ($files as $file) {
        if ($file->isDir()) {
            continue;
        }
        require_once $file->getRealPath();
    }
}

return $app;