Upgrade symfony 2.3 LTS to 2.6

Question

I would like upgrade my symfony app which is based on symfony 2.3. I want to use the new feature with the bootstrap theme for forms.

I never make an symfony upgrade before so I read this chapter from symfony cookbook.

http://symfony.com/doc/current/cookbook/upgrading.html

After that, I have made changes in my "composer.json" and type "composer update symfony/symfony", but I get the following error messages

Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Problem 1
- don't install symfony/event-dispatcher 2.6.x-dev|don't install symfony/symfony v2.6.3
- don't install symfony/symfony v2.6.3|remove symfony/event-dispatcher 2.6.x-dev
- Installation request for symfony/symfony 2.6.3 -> satisfiable by symfony/symfony[v2.6.3].
- Installation request for symfony/event-dispatcher == 2.6.9999999.9999999-dev -> satisfiable by symfony/event-dispatcher[2.6.x-dev].

My "composer.json":

{
    "name": "symfony/framework-standard-edition",
    "license": "MIT",
    "type": "project",
    "description": "The \"Symfony Standard Edition\" distribution",
    "autoload": {
        "psr-0": { "": "src/" }
    },
    "require": {
        "php": ">=5.3.3",
        "symfony/symfony": "2.6.*",
        "doctrine/orm": "~2.2,>=2.2.3",
        "doctrine/doctrine-bundle": "1.2.*",
        "twig/extensions": "1.0.*",
        "symfony/assetic-bundle": "2.3.*",
        "kriswallsmith/assetic": "1.1.2",
        "symfony/swiftmailer-bundle": "2.3.*",
        "symfony/monolog-bundle": "2.4.*",
        "sensio/distribution-bundle": "2.3.*",
        "sensio/framework-extra-bundle": "2.3.*",
        "sensio/generator-bundle": "2.3.*",
        "incenteev/composer-parameter-handler": "~2.0",
        "knplabs/knp-menu": "2.0.*@dev",
        "knplabs/knp-menu-bundle": "2.0.*@dev",
        "symfony/event-dispatcher": "2.6.*@dev",
        "knplabs/doctrine-behaviors": "dev-master",
        "a2lix/translation-form-bundle": "dev-master",
        "knplabs/knp-paginator-bundle": "~2.4",
        "jms/serializer-bundle": "~0.13"
    },
    "scripts": {
        "post-install-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile"
        ],
        "post-update-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile"
        ]
    },
    "config": {
        "bin-dir": "bin"
    },
    "minimum-stability": "stable",
    "extra": {
        "symfony-app-dir": "app",
        "symfony-web-dir": "web",
        "incenteev-parameters": {
            "file": "app/config/parameters.yml"
        },
        "branch-alias": {
            "dev-master": "2.3-dev"
        }
    }
}

Can someone give me a tip?

Answer 1

You shouldn't have to manually specify the event dispatcher at all. Remove that, then take a look at this file:

https://github.com/symfony/symfony-standard/blob/2.6/composer.json

Make sure your composer dependencies match everything. Also make sure you have "dev-master": "2.6-dev" under branch-alias