Composer Install Verbose Output

composer.json

{
    "name": "phindmarsh/composer-test",
    "description": "Testcase for checking dependencies bug",
    "require": {
        "silex/silex": "dev-master#279c773342c6c4d141ebd5236b18518c96505e00"
    },
    "authors": [
        {
            "name": "Patrick Hindmarsh",
            "email": "patrick@hindmar.sh"
        }
    ]
}

output.log

$ composer install -vvv
Reading ./composer.json
Loading config file /Users/patrick/.composer/config.json
Loading config file /Users/patrick/.composer/auth.json
Loading config file ./composer.json
Executing command (CWD): git describe --exact-match --tags
Executing command (CWD): git branch --no-color --no-abbrev -v
Executing command (CWD): hg branch
Executing command (CWD): svn info --xml
Reading /Users/patrick/.composer/composer.json
Loading config file /Users/patrick/.composer/config.json
Loading config file /Users/patrick/.composer/auth.json
Loading config file /Users/patrick/.composer/composer.json
Loading config file /Users/patrick/.composer/auth.json
Executing command (CWD): git describe --exact-match --tags
Executing command (CWD): git branch --no-color --no-abbrev -v
Executing command (CWD): hg branch
Executing command (CWD): svn info --xml
Loading composer repositories with package information
Downloading https://packagist.org/packages.json
Writing /Users/patrick/.composer/cache/repo/https---packagist.org/packages.json into cache
Installing dependencies (including require-dev)
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2013.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2014.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2014-07.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2014-10.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2015-01.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-2015-04.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-archived.json from cache
Downloading https://packagist.org/p/provider-latest$31349a549f38107c7f7dcaf7fa0b301ffceacbbb768d5c959cfcacb30e3cd515.json
Writing /Users/patrick/.composer/cache/repo/https---packagist.org/p-provider-latest.json into cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-silex$silex.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-pimple$pimple.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$event-dispatcher.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$http-foundation.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$http-kernel.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$routing.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$debug.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-psr$log.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-silex$api.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-silex$providers.json from cache
Reading /Users/patrick/.composer/cache/repo/https---packagist.org/provider-symfony$config.json from cache
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for silex/silex dev-master#279c773342c6c4d141ebd5236b18518c96505e00 -> satisfiable by silex/silex[dev-master].
    - silex/silex dev-master requires php >=5.5.9 -> your PHP version (5.4.29) does not satisfy that requirement.