Slim Error Application after connection

Hello, I’m trying to make an API. I’ve follow a tutorial in OpenClassRoom to make request with MySQL, and I want an API with Slim.
So I receive the answer of the connexion, but when I want to recover data from a get I have a “Slim Application Error” And I don’t know what to do with that.
I’m using MAMP instead of "php -S localhost:8080 -t public public/index.php " because I have the good connection with my database.
I show you my API:

use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;

require '/Users/kravennagen/Downloads/Api/api/racehistory/vendor/autoload.php';

$app = new \Slim\App();
echo "hello";
    $bdd = new PDO('mysql:host=localhost;dbname=racehistory;charset=utf8', 'root', 'root', array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
    echo "connexion...";
catch(Exception $e){
    die('Erreur connexion BDD:' . $e->getMessage());
echo "avant le get";
$app->get('/connexion/{identifiant}/{password}', function($login, $pass){
	$reponseMail = $bdd->query('SELECT mail FROM user');
	$reponsePass = $bdd->query('SELECT password FROM user');
  echo "test1";
	While($donnees = $reponseMail->fetch() && $donnees = $reponsePass->fetch()){
		if($donnees['mail'] == $login && $donnees['password'] == $pass){
      echo "true";
			return true;
      echo "false";
			return false;

$app->get("/register/{identifiant}/{password}", function($login, $pass){
	$add = 'INSERT INTO user(mail, password) VALUES ($login, $pass)';

	if(!preg_match("#^[a-z0-9._-]+@[a-z0-9._-]{2,}\.[a-z]{2,4}$#", $login))
	   $errors['mail'] = 'adresse mail non valide';

    else if (!preg_match("#^(?=.*[A-Z])(?=.*[a-zA-Z])(?=.*\d)([\w]{8,15})$#", $pass))
	   $errors['password'] = "le mot de passe n'est pas conforme(majuscule au debut, de 8 a 15 caractères)";

	else if($bdd->exec($add) === false){
		echo "User bien ajouté la base de donnée";

Thank you for your help !
EDIT: I change $app-> to $bdd-> and I don’t have any error now, but I don’t receive the answer “true” or “false”