composer: File could not be downloaded behind a proxy

Hi,

I can’t download any git repos behind a proxy with composer since few days. Composer can update itselfs, but no other git repos.

For example:

$ php composer.phar create-project symfony/framework-standard-edition path/ 2.2.1

results in:

[Composer\Downloader\TransportException]
The "https://api.github.com/repos/symfony/symfony-standard/zipball/v2.2.1" file could not be downloaded (HTTP/1.0 500 Internal Server Error)

System configuration:

• configured enviroment http_proxy & https_proxy
• PHP 5.4.14
• Composer 81d55544f714cca03d5eb784d67a06f8148bcb15

The proxy configuration works fine (Mozilla, Thunderbird, …). Downloading the file with wget or curl works too:

$ wget https://api.github.com/repos/symfony/symfony-standard/zipball/v2.2.1

Any advice?