I kept getting this error:
pear list-all File http://pear.php.net:80/rest/c/categories.xml not valid (received: HTTP/1.0 407 Proxy Authentication Required )
The error was because my proxy required an authentication. To use PEAR behind a proxy that requires authentication use this:
pear config-set http_proxy http://username:password@yourproxy:80
You can change 80 to the port of your proxy.