php使用curl下载https资源文件如何实现?

首先我们先了解一下php curl

如果开启了IPv6，curl默认会优先解析 IPv6，在对应域名没有 IPv6 的情况下，会等待 IPv6 dns解析失败 timeout 之后才按以前的正常流程去找 IPv4

在程序中我对curl获取内容都作了较为严格的超时限制，所以就会造成无法获取内容的问题。

php的curl设置方法如下：

<?php
/**
* IPV6下curl超时问题
*/
$ch = curl_init();
curl_setopt ($ch, CURLOPT_URL, $url);
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, true);
//设置curl默认访问为IPv4
if(defined('CURLOPT_IPRESOLVE') && defined('CURL_IPRESOLVE_V4')){
curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
}
//设置curl请求连接时的最长秒数，如果设置为0，则无限
curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
//设置curl总执行动作的最长秒数，如果设置为0，则无限
curl_setopt ($ch, CURLOPT_TIMEOUT,$timeout*3);
$file_contents = curl_exec($ch);
curl_close($ch);

以下是在网上搜索的一个实例：

$url = 'https://www.xxx.com/xxx.mp3';

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 20);

var_dump(curl_error($ch));

提示错误:SSL: certificate verification failed (result: 5)

然后网上搜了一大片：最多的解决方法是加上如下代码:

curl_setopt ($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt ($ch, CURLOPT_SSL_VERIFYHOST, false);

加上之后又报错：

SSL: CA certificate set, but certificate verification is disabled

该如何解决？？？？

<?php
$urls = [
    "https://cdn.XXX.com/lion-2016620__340.jpg 1x, 
     https://cdn.XXX.com/lion-2016620__480.jpg",
    "https://cdn.XXX.com/architecture-2083687__340.jpg 1x,             
     https://cdn.XXX.com/architecture-2083687__480.jpg",
    "https://cdn.XXX.com/reptile-2042906__340.jpg 1x, 
     https://cdn.XXX.com/reptile-2042906__480.jpg"
];

foreach ($urls as $k => $v) {
     if (!empty($v) && preg_match("~^http~i", $v)) {
        $nurl[$k] = trim(str_replace(' ', "%20", $v));
        $curl[$k] = curl_init($nurl[$k]);
        curl_setopt($curl[$k], CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
        curl_setopt($curl[$k], CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($curl[$k], CURLOPT_HEADER, 0);
        curl_setopt($curl[$k], CURLOPT_CONNECTTIMEOUT, 20);
        curl_setopt($curl[$k], CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($curl[$k], CURLOPT_SSL_VERIFYHOST, false);        
        if (!isset($handle)) {
           $handle = curl_multi_init();
        }
        curl_multi_add_handle($handle, $curl[$k]);
      }
      continue;
}
$active = null;
do {
   $mrc = @curl_multi_exec($handle, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);
   while ($active && $mrc == CURLM_OK) {
       if (curl_multi_select($handle) != -1) {
          do {
             $mrc = curl_multi_exec($handle, $active);
          } while ($mrc == CURLM_CALL_MULTI_PERFORM);
       }
   }

foreach ($curl as $k => $v) {
   var_dump(curl_error($curl[$k]));
}

以上解决方法按理来说应该没有问题，但依然报错。最后解决方法：

curl_setopt($curl[$k], CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);

改成：

curl_setopt($curl[$k], CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V6);

原文地址https://segmentfault.com/q/1010000008502236