OpenSSL错误消息：错误：14090086：SSL例程：SSL3_GET_SERVER_CERTIFICATE：证书验证失败

Question

我有这样的错误：

A PHP Error was encountered

Severity: Warning

Message: file_get_contents(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

使用XAMPP并使用codeigniter。可能有人知道这是什么问题？提前谢谢

这是我运行的代码

$url = "graph.facebook.com/".$user_profile['id']."/…;; 
$data = file_get_contents($url); 
$fp = fopen("images/results/img".$user_profile['id'].".jpg","wb"); 
if (!$fp) 
    exit; 

fwrite($fp, $data); 
fclose($fp);