php .env with Docker

To add phpdotenv, I am supposed to run the following terminal command:

composer require vlucas/phpdotenv

But I'm not exactly sure which folder I should be running the command.

My folder structure looks like this:

SITE
--> www
   --> css
   --> include
       - database.php
   - index.php
docker-compose.yml
dockerfile

When I run the composer command from the main SITE folder, it creates a folder called Vendor, as well as a composer.json file looks like this:

{
"require": {
    "vlucas/phpdotenv": "^5.6"
  }
}

So now the structure looks like this:

SITE
--> www
   --> css
   --> include
       - database.php
   - index.php
--> vendor
- composer.json
- composer.lock
- docker-compose.yml
- dockerfile

So now I can create a .env file within my www folder with the other webfiles, which looks like this:

DATABASE_HOST=db
DATABASE_NAME=myDb
DATABASE_USER=user
DATABASE_PASS=test

So in my database.php file, I try to pass the info from my .env file:

<?php
  require __DIR__ . "/vendor/autoload.php";

  $dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
  $dotenv->load();   
 
  $dbhost = $_ENV["DATABASE_HOST"];
  $dbname = $_ENV["DATABASE_NAME"];
  $dbuser = $_ENV["DATABASE_USER"];
  $dbpass = $_ENV["DATABASE_PASS"];   

  try{
    $dbc = new PDO("mysql:dbname=$dbname;host=$host;port=3306;user=$dbuser;pass=$dbpass");
    $dbc->SetAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  } catch(PDOException $e) {
    echo "Conneciton failed: " . $e->getMessage() . "<br/>";
  }  
?>

After doing all of the above, I am getting the below error:

Warning: require(/var/www/html/include/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/html/include/database.php on line 2

Fatal error: require(): Failed opening required '/var/www/html/include/vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /var/www/html/include/database.php on line 2

I tried adjusting the vendor path in the database.php file, but I still get the same error.

I tried running the composer command inside the www folder, but I still get the same error.

What did I do wrong and how do I fix it?

I no longer got the error when I moved the Vendor folder, the composer.json and composer.lock into the WWW folder.