VSC / PHP Intelephense does not know postgres typings

Question

I am working on a PHP class that provides functions for my postgres database. My class Database looks like this:

<?php

declare(strict_types=1);

namespace App\Services\Database;

include_once('../server/Config.php');
include_once('../server/App/Services/Database/DatabaseConfiguration.php');

use \App\Services\Database\DatabaseConfiguration;

class Database
{

    private DatabaseConfiguration $config;
    private \PgSql\Connection|false $connection;

    public function __construct(?string $host, ?int $port, ?string $dbName, ?string $user, ?string $password)
    {
        $this->config = new DatabaseConfiguration($host, $port, $dbName, $user, $password);
    }

    public function connect(): bool
    {
        $this->connection = pg_connect($this->config->connectionInfo());
        if ($this->connection) {
            return true;
        } else {
            return false;
        }
    }
}

So nothing fancy, but my IDE (Visual Studio Code & PHP Intelephense) throws an error when it comes to the connection with the database.

Undefined type 'PgSql\Connection'.

This line forces the error:

private \PgSql\Connection|false $connection;

According to the documentation (here), the function pg_connect returns the type PgSql\Connection|false. Because my class is wrapped in a namespace I added a \ in front. But both notations throw the error.

Before I was using PG I used MySql and with that I had no issue when it comes to typing.

So how can I run my IDE with PG typings?

Setup: Win10, PHP 8.1.2, PHP Intelephense v1.8.2

Edit: In the extension settings there is this tab:

Intelephense: Stubs Configure stub files for built in symbols and common extensions. The default setting includes PHP core and all bundled extensions.

-> pgsql is added there.