Slow updating of composer dependencies, despite --prefer-dist flag

Question

Why does it take up to two minutes for my composer dependencies to update, even when there have been no changes?

A popular suggestion is to append the --prefer-dist flag:

php composer.phar update --prefer-dist

But this makes no difference in my case. Below is my composer.json file – am I missing something obvious?

{
    "name": "my-namespace/symfony",
    "type": "project",
    "description": "",
    "require": {
        "php": ">=5.3.3",
        "symfony/symfony": "2.3.*",
        "doctrine/orm": ">=2.2.3,<2.4-dev",
        "doctrine/doctrine-bundle": "1.2.*",
        "twig/extensions": "1.0.*",
        "symfony/assetic-bundle": "2.3.*",
        "symfony/monolog-bundle": "2.3.*",
        "sensio/framework-extra-bundle": "2.3.*",
        "sensio/generator-bundle": "2.3.*",
        "sensio/distribution-bundle": "2.2.*",
        "my-namespace/my-bundle": "1.0.*"
    },
   "repositories": [
        {
            "type": "vcs",
            "url": "http://username:[email protected]/my-bundle.git"
        }
    ],    
    "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"
        ]
    },
    "config": {
        "bin-dir": "bin"
    },
    "minimum-stability": "dev",
    "extra": {
        "symfony-app-dir": "app",
        "symfony-web-dir": "web",
        "branch-alias": {
            "dev-master": "2.3-dev"
        }
    }
}

Answer 1

This problem is often related to xdebug being loaded in your CLI environment. (It doesn't matter if xdebug is enabled or not.)

You can check whether xdebug is enabled using one of the followinc commands.

// Unix
php -m | grep xdebug
// Windows
php -m | findstr xdebug

Further information on what operations take so long can be gained by enabling maximum verbosity and profiling information. (Replace install with update if you are updating the packages.)

composer install --prefer-dist -vvv --profile