app/config.php

<?php
    ini_set("display_errors",1);
    ini_set("display_startup_errors",1);
    error_reporting(E_ALL);

    define("DB_NAME", getenv("DB_NAME"));
    define("DB_USER", getenv("DB_USER"));
    define("DB_PASSWORD", getenv("DB_PASSWORD"));
    define("DB_HOST", getenv("DB_HOST"));

    $conn = @mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

    if (!$conn) {
        die("No se pudo conectar: " . mysqli_connect_error());
    }
    else{
        echo("<h1>Conexión correcta!</h1>");
    }
?>