Parse database dsn

[fiedsch]

Maybe use something like the following extract a parameter from the DATABASE_URL:

<?php
require ('/path/to/the/contao/installation/we/want/to/backup/vendor/autoload.php');

use Doctrine\DBAL\Tools\DsnParser;
use Doctrine\DBAL\Exception\MalformedDsnException;

$dsn = $argv[1] ?? '';
$parameter = $argv[2] ?? '';

if ('' === $dsn || '' === $parameter) {
    fwrite(STDERR, 'required parameters are missing');
    exit(1);
}

$dsnParser = new DsnParser();
try {
    $connectionParams = $dsnParser->parse($dsn);

} catch (MalformedDsnException $e) {
    fwrite(STDERR, $e->getMessage());
    exit(2);
}

if (!isset($connectionParams['port'])) {
    $connectionParams['port'] = 3306;
}

if (!isset($connectionParams[$parameter])) {
    fwrite(STDERR,  'parameter not set');
    exit(3);
}

echo $connectionParams[$parameter];
exit(0);