win7本地安装laravel,wamp2.4安装OK，composer安装到第四部这里就不解

Connection Error [ERR_CONNECTION]: Unable to connect to getcomposer.org

Request to https://getcomposer.org/installer failed with errors:
Php_network_getaddresses: getaddrinfo failed: 在数据库查找中出现一个不可恢复的错误。 . Failed to open stream: php_network_getaddresses: getaddrinfo failed: 在数据库查找中出现一个不可恢复的错误。