Symfony2安装程序问题(2.7)

我正在尝试安装SF2 2.7版本，当我按照这里的步骤安装Symfony Installer:

php -r "readfile('http://symfony.com/installer');" > symfony 

它不安装SF2并给出错误:

G:'>symfony new alfa
'symfony' is not recognized as an internal or external command, 
 operable program or batch file.

当我尝试这个命令时:

G:'>php symfony
Warning: readfile(): php_network_getaddresses: getaddrinfo failed: This is 
usually a temporary error during hostname resolution and means that the 
local server did not receive a response from an authoritative server.  in 
Command line code on line 1
Warning: readfile(http://symfony.com/installer): failed to open stream:
php_network_getaddresses: getaddrinfo failed: This is usually a temporary 
error during hostname resolution and means that the local server did not 
receive a response from an authoritative server.  in Command line code on 
line 1

我在Symfony网站上找不到任何关于其他安装方法的帮助。