composer/src/Composer/Command/UpdateCommand.php

<?php

/*
 * This file is part of Composer.
 *
 * (c) Nils Adermann <naderman@naderman.de>
 *     Jordi Boggiano <j.boggiano@seld.be>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Composer\Command;

use Composer\Installer;
use Composer\Script\EventDispatcher;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Input\InputOption;
use Symfony\Component\Console\Output\OutputInterface;

/**
 * @author Jordi Boggiano <j.boggiano@seld.be>
 */
class UpdateCommand extends Command
{
    protected function configure()
    {
        $this
            ->setName('update')
            ->setDescription('Updates your dependencies to the latest version, and updates the composer.lock file.')
            ->setDefinition(array(
                new InputOption('prefer-source', null, InputOption::VALUE_NONE, 'Forces installation from package sources when possible, including VCS information.'),
                new InputOption('dry-run', null, InputOption::VALUE_NONE, 'Outputs the operations but will not execute anything (implicitly enables --verbose).'),
                new InputOption('install-recommends', null, InputOption::VALUE_NONE, 'Also install recommended packages.'),
                new InputOption('install-suggests', null, InputOption::VALUE_NONE, 'Also install suggested packages.'),
            ))
            ->setHelp(<<<EOT
The <info>update</info> command reads the composer.json file from the
current directory, processes it, and updates, removes or installs all the
dependencies.

<info>php composer.phar update</info>

EOT
            )
        ;
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $composer = $this->getComposer();
        $io = $this->getApplication()->getIO();
        $eventDispatcher = new EventDispatcher($composer, $io);
        $install = Installer::create($io, $composer, $eventDispatcher);

        $install
            ->setDryRun($input->getOption('dry-run'))
            ->setVerbose($input->getOption('verbose'))
            ->setPreferSource($input->getOption('prefer-source'))
            ->setInstallRecommends($input->getOption('install-recommends'))
            ->setInstallSuggests($input->getOption('install-suggests'))
            ->setUpdate(true)
        ;

        return $install->run();
    }
}