Ndtyjky

I have a project that is on Symfony 2.1 and need to upgrade to 4.0
Do you know how is the best way?
Can I just upgrade from 2.1 to 4.0 directly? or is better to migrate first from 2.1 to 3.0 and then 4.0...
Do you know what's teh best way?
Thanks so much!

You should not upgrade directly. Instead upgrade to 2.8 first, fix all deprecations using a tool like deprecation-detector. You might want to do this in smaller steps. There were quite a few deprecations and even some BC-breaks back then, especially around the form component, and reading the changelogs between versions is important to keep track of these changes. This doesn't sound like much, but it can already be a very tedious task, but it's worth it.

Once you have moved to 2.8 you can make the switch to Symfony 3.4, again fix all deprecations. There was one security related BC-break, that's easy to fix. Other than that upgrading from 2.8 to 3.4 should be easier than upgrading to 2.8.

From 3.3 on there is a persisted deprecation log you can use to fix all deprecations introduced during the minor releases. When you make it to 3.4 you are fine for a while. This is a long term support-version, so you will not require major updates until next year.

4.0 does not receive bug fixes and security fixes are only available until January 2019, so if you want to switch to the next major version I suggest going to 4.2 and then keep updating regularly (every 6 months when a new minor release comes out). If this sounds like too much of a hassle, I recommend staying on 3.4 for a while and then upgrade to the next LTS release using the same steps as above.

Especially when upgrading Symfony 3.4 to 4.x you could also look at a tool called rector which can do automatic upgrades for you. As far as I can tell it does not support all changes that happened, but it will at least make some of the deprecation-changes easier by automating them for you.

edit: Also keep in mind that when you upgrade you will also have to upgrade the bundles you use and some of them might not even support 3.x or 4.x. Addressing those by either doing the manual config changes or replacing them is probably the most annoying bit of the work. Using composer why and composer why-not to figure out why composer won't upgrade certain packages or even Symfony itself will be very useful.

Thanks for replying back. I'll try yo start upgrading to 2.8.0 first, but there are a lot of conflicts of versions in my composer.json, currently I have this:

"require": {
"php": ">=5.3.3",
"symfony/symfony": "2.1.",
"doctrine/orm": ">=2.2.3,<2.4-dev",
"doctrine/doctrine-bundle": "1.0.",
"twig/extensions": "1.0.@dev",
"symfony/assetic-bundle": "2.1.",
"symfony/swiftmailer-bundle": "2.1.",
"symfony/monolog-bundle": "2.1.",
"sensio/distribution-bundle": "2.1.",
"sensio/framework-extra-bundle": "2.1.",
"sensio/generator-bundle": "2.1.",
"jms/security-extra-bundle": "1.2.",
"jms/di-extra-bundle": "1.1.",
"kriswallsmith/assetic": "1.1.@dev",
"hearsay/require-js-bundle":"*",
"symfony/options-resolver": "2.6",
"wsdl2phpgenerator/wsdl2phpgenerator": "3.3"
},
"scripts": {
"post-install-cmd": [
"SensioBundleDistributionBundleComposerScriptHandler::buildBootstrap",
"SensioBundleDistributionBundleComposerScriptHandler::clearCache",
"SensioBundleDistributionBundleComposerScriptHandler::installAssets",
"SensioBundleDistributionBundleComposerScriptHandler::installRequirementsFile"
],
"post-update-cmd": [
"SensioBundleDistributionBundleComposerScriptHandler::buildBootstrap",
"SensioBundleDistributionBundleComposerScriptHandler::clearCache",
"SensioBundleDistributionBundleComposerScriptHandler::installAssets",
"SensioBundleDistributionBundleComposerScriptHandler::installRequirementsFile"
]
},
"extra": {
"symfony-app-dir": "app",
"symfony-web-dir": "web"
}

Do you know if there is a way to know which versions shoukd I have to put after require section? Thanks!

Sorry, sending the composer.json code again:

{

"name": "symfony/framework-standard-edition",

"description": "The "Symfony Standard Edition" distribution",

"autoload": {

    "psr-0": { "": "src/" }

},

"require": {

    "php": ">=5.3.3",

    "symfony/symfony": "2.1.*",

    "doctrine/orm": ">=2.2.3,<2.4-dev",

    "doctrine/doctrine-bundle": "1.0.*",

    "twig/extensions": "1.0.*@dev",

    "symfony/assetic-bundle": "2.1.*",

    "symfony/swiftmailer-bundle": "2.1.*",

    "symfony/monolog-bundle": "2.1.*",

    "sensio/distribution-bundle": "2.1.*",

    "sensio/framework-extra-bundle": "2.1.*",

    "sensio/generator-bundle": "2.1.*",

    "jms/security-extra-bundle": "1.2.*",

    "jms/di-extra-bundle": "1.1.*",

    "kriswallsmith/assetic": "1.1.*@dev",

    "hearsay/require-js-bundle":"*",

    "symfony/options-resolver": "2.6",

    "wsdl2phpgenerator/wsdl2phpgenerator": "3.3"

},

"scripts": {

    "post-install-cmd": [

        "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": [

        "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::buildBootstrap",

        "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache",

        "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installAssets",

        "Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::installRequirementsFile"

    ]

},

"extra": {

    "symfony-app-dir": "app",

    "symfony-web-dir": "web"

}

}