Upgrading Symfony 3.4 to 4.x with Flex - Composer Problems - symfony

Question

I have a Symfony 3.4 project I'm trying to upgrade to 4.x with Flex but I'm falling at the first hurdle.
With the output of Composer this verbose I assume the answer is staring me straight in the face, but I'm not seeing it. What do I need to do? I've deleted everything in vendor, deleted my composer.lock file, cleared composer cache, etc.
composer.json
{
"type": "project",
"license": "proprietary",
"require": {
"php": "^7.1.3",
"ext-ctype": "*",
"ext-iconv": "*",
"sensio/framework-extra-bundle": "^5.5",
"symfony/console": "4.4.*",
"symfony/dotenv": "4.4.*",
"symfony/flex": "^1.3.1",
"symfony/framework-bundle": "4.4.*",
"symfony/monolog-bundle": "^3.5",
"symfony/orm-pack": "^1.0",
"symfony/profiler-pack": "^1.0",
"symfony/twig-pack": "^1.0",
"symfony/yaml": "4.4.*",
"friendsofsymfony/jsrouting-bundle": "^2.5",
"friendsofsymfony/user-bundle": "~2.0",
"stof/doctrine-extensions-bundle": "^1.3",
"symfony/swiftmailer-bundle": "^2.6.4",
"ext-json": "*"
},
"require-dev": {
"symfony/debug-pack": "^1.0",
"phpstan/extension-installer": "^1.0",
"phpstan/phpstan": "^0.12.19",
"phpstan/phpstan-doctrine": "^0.12.10",
"phpunit/phpunit": "^7.5",
"symfony/phpunit-bridge": "^3.0"
},
"config": {
"preferred-install": {
"*": "dist"
},
"sort-packages": true
},
"autoload": {
"psr-4": {
"App\\": "src/"
}
},
"autoload-dev": {
"psr-4": {
"App\\Tests\\": "tests/"
}
},
"scripts": {
"auto-scripts": {
"cache:clear": "symfony-cmd",
"assets:install %PUBLIC_DIR%": "symfony-cmd"
},
"post-install-cmd": [
"#auto-scripts"
],
"post-update-cmd": [
"#auto-scripts"
]
},
"extra": {
"symfony": {
"allow-contrib": false,
"require": "4.4.*"
}
}
}
Tried to composer install with:
php -d memory_limit=-1 /usr/local/bin/composer install
And it spews all this out (too big to paste here): https://pastebin.com/KLVRkYdF
Saw something elsewhere about needing to install Flex on its own first, so I tried this:
php -d memory_limit=-1 /usr/local/bin/composer update symfony/flex --no-plugins --no-scripts
But got the following error (too big to paste here): https://pastebin.com/KxG2siZi

Answer 1

The problem is that you haven't updated symfony/swiftmailer-bundle - as given in the composer.json, you tried to install at most v2.6.7 which requires symfony/http-kernelin v2.7 or v3.x. This is not compatible with symfony/framework-bundle in v4.4, as this requires symfony/http-kernel to be of that same v4.4 branch.
Conclusion: also update symfony/swiftmailer-bundle to at least v3.1 which is the first one to be compatible with Symfony v4.

Answer 2

I also had a lot of issues with composer, packageversions and memory limits in the past.
Package vesions:
Set all symfony packages to the version "*" if yout dont require a specific Version at this point. Thisway composer will select the one suitable to your configured symfony version.
Memory limit:
Which IDE are you using? Which PHP Version? 32 or 64 bit? Try running the commany outside of the IDE and see what happens. Alternatively try the symfony command.