“PDOException: could not find driver” inside docker container where PDO modules exist

I want to run php-fpm in a docker container, but get an error message after starting the container:

Fatal error: Uncaught PDOException: could not find driver.

I use php7.4 with event engine and a postgres database in a separate container (I use docker-compose to start them all) and are working on ubuntu20.04.

The weird thing is: My collegues installed the same stuff without having this error, so the error cannot come from an incorrect docker file.

What I tried so far:

• I can connect to the database with psql from the shell.
• I printed out all modules that are loaded in the container, and they include pdo and pdo_pgsql.

The error refers to this method:

    public function pdoConnection(): PDO
    {
        /** @var PDO $pdo */
        $pdo = $this->makeSingleton(PDO::class, function () {
            $this->assertMandatoryConfigExists('pdo.dsn');
            $this->assertMandatoryConfigExists('pdo.user');
            $this->assertMandatoryConfigExists('pdo.pwd');

            return new PDO(
                $this->config()->stringValue('pdo.dsn'),
                $this->config()->stringValue('pdo.user'),
                $this->config()->stringValue('pdo.pwd'),
                [

                    // the next line is the line the error message refers to
                    PDO::ATTR_PERSISTENT => true,

                    // This is necessary due to the way pgBouncer handles (or not handles) prepared statements.
                    // See https://www.pgbouncer.org/faq.html#how-to-use-prepared-statements-with-transaction-pooling
                    PDO::ATTR_EMULATE_PREPARES => true,
                ]
            );
        });

        return $pdo;
    }

I checked pdo.dns, pdo.user and pdo.pwd, they are all correct. I defined DNS via

DNS = "pgsql:host=HOSTNAME port=5432 dbname=DATABASENAME"

The docker file includes

docker-php-ext-install pdo_pgsql

Answer

It was the DNS string, the quotation marks are wrong. It works with this:

DNS = pgsql:host=HOSTNAME;port=5432;dbname=DATABASENAME