Google App Engine - PHP - Class not found - php

Question

i've problem with Google App Engine and PHP.
I use Slim framweork for a sample project to test App Engine (currently I use AWS).
I created a simple Slim app and deployed it to App engine and to AWS. On AWS it runs fine, but on App Engine i get "class not found error":
2018/07/29 21:38:15 [error] 9#9: *1 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Class 'projectName\Middleware\Logging' not found in /app/public/index.php:21
thrown in /app/public/index.php on line 51" while reading response
header from upstream, client: 172.17.0.4, server: , request: "GET //
HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host:
"projectName-183713.appspot.com"
/public/index.php
<?php
namespace projectName;
require __DIR__ . '/../vendor/autoload.php';
session_start();
$settings = require __DIR__ . '/../src/settings.php';
$app = new \Slim\App($settings);
require __DIR__ . '/../src/dependencies.php';
require __DIR__ . '/../src/middleware.php';
require __DIR__ . '/../src/routes.php';
require __DIR__ . '/../src/projectName/Routes/route_login.php';
require __DIR__ . '/../src/projectName/Routes/route_user.php';
require __DIR__ . '/../app/routes.php';
require __DIR__ . '/../app/database.php';
use \projectName\Middleware\Logging;
use \projectName\Middleware\Authentication;
$logging = new Logging();
$auth = new Authentication($app->getContainer()->get('router'));
$app->add($logging);
$app->add($auth);
$app->get('/hello/{name}', function ($request, $response, $args) {
echo 'Hello';
return $response;
});
$app->run();
/src/projectName/Middleware/Logging.php
<?php
namespace projectName\Middleware;
class Logging{
public function __invoke($request, $response, $next)
{
$response = $next($request, $response);
return $response;
}
}
app.yaml
runtime: php
env: flex
runtime_config:
document_root: public
handlers:
- url: .*
script: index.php
- url: /(.+\.php)$
script: \1
__DIR__ . '/../vendor/autoload.php'
"autoload": {
"psr-4": {
"\\projectName\\": "src/projectName",
"\\projectName\\Models\\": "src/projectName/Models",
"\\projectName\\Middleware\\": "src/projectName/Middleware"
}
}

Answer 1

The problem was with psr-4 in composer.json.
App Enginen doesn't work with two backslash in the route. So, the solution is:
"\\projectName\\": "src/projectName",
=>
"projectName\\": "src/projectName",
AWS and local dev (standard php docker) works fine with double backslash, but App engine not.