PHP.ini默认配置下，用file_get_contents读取https的链接，就会如下错误：
Warning: fopen() [function.fopen]: Unable to find the wrapper "https" - did you forget to enable it when
“Message: file_get_contents(): Unable to find the wrapper “https” - did you forget to enable it when you configured PHP?”
Message: file_get_contents(https://api.weixin.qq.com/sns/oauth2/acces****):
