How can developers ensure that session_start is only called once at the beginning of a PHP script?

To ensure that session_start is only called once at the beginning of a PHP script, developers can use a conditional check to see if the session has already been started before calling session_start. This can be done by checking if the session_id is empty or if the session_status is not PHP_SESSION_ACTIVE. By implementing this check, developers can prevent multiple calls to session_start within the same script execution.

if (session_status() == PHP_SESSION_NONE) {
    session_start();
}