第二个就快到了。

我很确定打电话给

echo curl_error($curl);

curl的执行后将给您：SSL证书问题：无法获得本地颁发者证书

基本上有两种方法可以解决这个问题-

正确的方式

从下载cacert.pem文件https://curl.haxx.se/docs/caextract.html，将其保存在脚本可以访问的地方，并在curl_exec（）之前添加以下行；调用

    // Add certification atuhority info
    curl_setopt($curl, CURLOPT_CAINFO, './path/to/cacert.pem'); 

注意，这不适用于自签名SSL证书

快速修复

您可能希望使SSL检查"松散"。

    // disable SSL checks
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 2);

请注意，即使使用自签名SSL证书，这种方法也可以工作，但这样做被认为是不安全的。

我知道这个答案被接受已经有一段时间了，但它不太适合我的用例，所以我想添加它。在OP的示例中，他们有一个HTTPS url，其中包含一个SSL检查失败的证书。在我的例子中，我使用TCPDF将HTML转换为PDF，其中HTML包含一个img标记，该标记使用自签名证书对HTTPS服务器进行调用。TCPDF对$img_size = @getimagesize()的调用进行硬编码，因此不能用一些自定义函数替换它。

1.尽可能自定义上下文

适用于接受上下文的函数，如file_get_contents

<?php
// Create a read context that disables peer verification when used
$context = stream_context_create(array(
    'ssl' => array(
        'verify_peer' => false,
        'verify_peer_name' => false,
    )
));
// The self-signed server URL
$url = 'https://domain.tld/doc.png';
// Make this the global default context
stream_context_set_default($context);
$content = file_get_contents($url);
// OR use in a specific function call without changing global context
$content = file_get_contents($url, false, $context);

2.流包装器解决方案

使用GD库函数，包括getimagesize

<?php
// Unregister existing https handling
stream_wrapper_unregister('https');
// Register the custom handler
stream_wrapper_register('https', "HttpsInsecureStream", STREAM_IS_URL);
/**
 * Content is read with CURL into a tmpfile that is deleted as soon as the stream is closed
 */
class HttpsInsecureStream {
    public $context = null;
    public function __construct() {
        $this->context = tmpfile();
    }
    public function stream_open($path,$mode,$options,&$opened_path){
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_URL, $path);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0);
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0);
        fwrite($this->context, curl_exec($curl));
        rewind($this->context);
        curl_close($curl);
        return true;
    }
    public function stream_stat() {
        return fstat($this->context);
    }
    public function stream_seek($seek_offset, $seek_whence) {
        return (fseek($this->context, $seek_offset, $seek_whence) === 0);
    }
    public function stream_tell(){
        return ftell($this->context);
    }
    public function stream_read($read_buffer_size){
        $result = fread($this->context, $read_buffer_size);
        return $result;
    }
    public function stream_write($write_data){
        return fwrite($this->context, $write_data);
    }
    public function stream_eof(){
        return feof($this->context);
    }
    public function stream_close () {
        return fclose($this->context);
    }
    public function stream_flush () {
        return fflush($this->context);
    }
    public function url_stat ($path ,$flags ) {
        return $this->stream_stat();
    }
    /* These functions are not implemented in this example, not sure if 
     * any of them make sense in the context of an HTTPS request.
     * Including them as a reference for the other handler functions that
     * are possible to implement in custom stream handler classes.
     */
    /*
    public function dir_closedir() { echo 1; return true; }
    public function dir_opendir ($path , $options ) { echo 2; return true; }
    public function dir_readdir () { echo 3; return true; }
    public function dir_rewinddir () { echo 4; return true; }
    public function mkdir ($path ,$mode ,$options ) { echo 5; return true; }
    public function rename ($path_from ,$path_to ) { echo 6; return true; }
    public function rmdir ($path ,$options ) { echo 7; return true; }
    public function stream_cast ($cast_as ) { echo 8; return $this->resource; }
    public function stream_lock ($operation ) { echo 'A'; return true; }
    public function stream_metadata ($path ,$option , mixed $value ) { echo 'B'; return true; }
    public function stream_set_option ($option ,$arg1 ,$arg2 ) { echo 'C'; return true; }
    public function stream_truncate ($new_size ) { echo 'D'; return true; }
    public function unlink ($path ) { echo 'E'; return true; }
    */
}

我想明确的是，上面的例子展示了如何实现这一点，但INSECURE。我在开发服务器上使用它，如果必须在生产中使用它，我会使用CURLOPT_CAINFO选项（请参阅上面的@Zenithies解决方案）。

参考：https://www.php.net/manual/en/class.streamwrapper.php