php下载远程文件

<?php
     $path = './upload/file/;
     if (!is_dir($path)) mkdir($path,777,true);
     $file_path = $path . time().rand(1,100000) . '.pdf';

     $curl = curl_init(); // 启动一个CURL会话
     curl_setopt($curl, CURLOPT_URL, $url);
     curl_setopt($curl, CURLOPT_HEADER, 0);
     curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
     curl_setopt($curl, CURLOPT_POSTFIELDS, $formData); 
     $tmpInfo = curl_exec($curl);
     //关闭URL请求
     curl_close($curl);
     file_put_contents($file_path,$tmpInfo);