PHP FPM Docker ZF1: The session has already been started. The session id must be set first

Question

In my dev environment, I'm trying to replace the old heavy Vagrant VM with Docker, using docker-compose :

version: '2'
services:
    nginx:
        build: ./containers/nginx
        networks:
            mm:
                ipv4_address: 172.25.0.101
        environment:
            APPLICATION_ENV: development
        extra_hosts:
            - "mysite.dev:127.0.0.1"
        ports:
            - 80:80
        links:
            - php
        volumes:
            - ../:/srv

    php:
        build: ./containers/php-fpm
        networks:
            mm:
                ipv4_address: 172.25.0.102
        volumes:
            - ../:/srv
        links:
            - memcached
        ports:
            - 9000:9000

    memcached:
        image: memcached:latest
        ports:
            - 1234:11211
        networks:
            mm:
                ipv4_address: 172.25.0.103

networks:
    mm:
        driver: bridge
        ipam:
            driver: default
            config:
                - subnet: 172.25.0.0/24

But the application is written with ZF1, and whenever I instantiate an Zend_Session_Namespace object just after Zend_Session::start() the following error appears:

Zend_Session_Exception: The session has already been started. The session id must be set first. in /srv/mm/vendor/zendframework/zendframework1/library/Zend/Session.php on line 667

I've tried it all, mouting a session path with VOLUME , changing the session.save_path , installing it all again and again, and nothing happens.

Answer 1

After spent a long debugging this issue I've found the answer for your question. On the second time you call Zend_Session::start() ZF will validate the session id by checking whether it was generated with proper hash_bits_per_character defined by php_ini setting session.hash_bits_per_character or not.

/**
 * From Zend_Session 
 */
protected static function _checkId($id)
{
    $saveHandler = ini_get('session.save_handler');
    if ($saveHandler == 'cluster') { // Zend Server SC, validate only after last dash
        $dashPos = strrpos($id, '-');
        if ($dashPos) {
            $id = substr($id, $dashPos + 1);
        }
    }

    $hashBitsPerChar = ini_get('session.hash_bits_per_character');
    if (!$hashBitsPerChar) {
        $hashBitsPerChar = 5; // the default value
    }
    switch($hashBitsPerChar) {
        case 4: $pattern = '^[0-9a-f]*$'; break;
        case 5: $pattern = '^[0-9a-v]*$'; break;
        case 6: $pattern = '^[0-9a-zA-Z-,]*$'; break;
    }
    return preg_match('#'.$pattern.'#', $id);
}

The problem is that for some reason the session id is generated with hash_bits_per_character = 5 instead of hash_bits_per_character = 4 . So, to solve this problem, all you need to do is force the session.hash_bits_per_character setting before calling Zend_Session::start() for the first time and Zend_Session will check the hash bits using the correct pattern:

Zend_Session::setOptions(['hash_bits_per_character' => 5]);