command "curl -s https://getcomposer.org/installer | php" didn't work with HTTP_PROXY on RH ES.

On a Red Hat Enterprise Linux Server we use this variable 

HTTP_PROXY=http://www-proxy.nl.blabla.com:8080

Then I try to install composer

curl -s https://getcomposer.org/installer | php

And got this message:

Downloading...
Download failed: php_network_getaddresses: getaddrinfo failed: Name or service not known
failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known

The problem was/is on line 275 of the installer.