Php versions – Legacy Symfony project: PHP Warning: session_start(): The session id is too long or contains illegal characters

I am trying to deploy a legacy Symfony 1.4 (actually Symfon 1.5 via FriendsOfSymfony1 [1]) project in a Vagrant Box with Ubuntu 18.x. My PHP version is 7.2.x (see [2]) Everything works fine, the site loads, but I get this error (and cannot complete the login to the legacy site):

[Fri Feb 07 14:51:53.880189 2020] [php7:warn] [pid 2831] [client 10.0.2.2:63895] PHP Warning: session_start(): The session id is too long or contains illegal characters, valid characters are a-z, A-Z, 0-9 and ‘-,’ in /home/vagrant/swdev/lib/vendor/lexpress/symfony1/lib/storage/sfSessionStorage.class.php on line 95, referer: http://127.0.0.1:8080/frontend_dev.php/registration/

[Fri Feb 07 14:51:53.880478 2020] [php7:warn] [pid 2831] [client 10.0.2.2:63895] PHP Warning: session_start(): Failed to read session data: files (path: /var/lib/php/sessions) in /home/vagrant/swdev/lib/vendor/lexpress/symfony1/lib/storage/sfSessionStorage.class.php on line 95, referer: http://127.0.0.1:8080/frontend_dev.php/registration/

There is already a discussion here: The session id is too long or contains illegal characters, valid characters are a-z, A-Z, 0-9 and '-,' But it does not solve my problem.

The relevant code snippet (line 95) is here:

https://github.com/FriendsOfSymfony1/symfony1/blob/d9e3f17e246ed90590c4e5175f1cec39f4a68254/lib/storage/sfSessionStorage.class.php#L95

The code that sets the session_id is in the same file, line 52 onward:

  public function initialize($options = null)
  {
    $cookieDefaults = session_get_cookie_params();

    $options = array_merge(array(
      'session_name'            => 'symfony',
      'session_id'              => null,      // <=============== HERE
      'auto_start'              => true,
      'session_cookie_lifetime' => $cookieDefaults['lifetime'],
      'session_cookie_path'     => $cookieDefaults['path'],
      'session_cookie_domain'   => $cookieDefaults['domain'],
      'session_cookie_secure'   => $cookieDefaults['secure'],
      'session_cookie_httponly' => isset($cookieDefaults['httponly']) ? $cookieDefaults['httponly'] : false,
      'session_cache_limiter'   => null,
    ), $options);

    // initialize parent
    parent::initialize($options);

This link mentions that it’s a PHP 7.1 issue (I have PHP 7.2!?), and that you cannot use null as session_id (like the code above does). So I changed

'session_id' => null,

to

'session_id' => '',

then I cleared cached via ./symfony cc, then restarted apache, but still: I get the PHP warning re session id.

Memcached related?

Maybe related: reviewing the legacy code, I realize that the session storage is defined in my factories.yml file like so:

(snip)

  storage:
    class: sfCacheSessionStorage
    param:
      session_name: prx
      cache: 
        class: sfMemcacheCache #[required] define the cache strategy
        param:
          servers: # Array of servers
            localserver:
              host: localhost # hostname or IP of mamcache server
              port: 11211 # default memcache port

(snip)

Memcached is already installed and running:

vagrant@ubuntu-bionic:~/swdev$ ps aux | grep -i memc
memcache  1002  0.0  0.3 424764  3036 ?        Ssl  13:50   0:01 /usr/bin/memcached -m 64 -p 11211 -u memcache -l 127.0.0.1 -P /var/run/memcached/memcached.pid
vagrant   3289  0.0  0.1  13136  1108 pts/0    S+   15:42   0:00 grep --color=auto -i memc

Footnotes

[1] Instead of Symfony 1.4 I am using an update from FriendsOfSymfony1

https://github.com/FriendsOfSymfony1/symfony1

[2] PHP Version

PHP 7.2.24-0ubuntu0.18.04.2