Laravel-snappy 在服务器执行的时候报如下错误，本地正常，求解？

以及如下半段
[============================================================] 100%
Counting pages (2/6)
[============================================================] Object 1 of 1
Resolving links (4/6)
[============================================================] Object 1 of 1
Loading headers and footers (5/6)
Printing pages (6/6)
[> ] Preparing
[============================================================] Page 1 of 1
Done
Exit with code 1 due to network error: UnknownNetworkError
QSslSocket: cannot call unresolved function CRYPTO_num_locks
QSslSocket: cannot call unresolved function CRYPTO_set_id_callback
QSslSocket: cannot call unresolved function CRYPTO_set_locking_callback
"
stdout: ""
command: /home/services/qtin-end-cms-x/vendor/h4cc/wkhtmltopdf-amd64/bin/wkhtmltopdf-amd64 --lowquality --
page-size 'a4' '/tmp/knp_snappy5a29036e53ac81.28775171.html' '/tmp/knp_snappy5a2906.pdf'.

遇到过类似问题。
wkhtmltopdf和OS的兼容性。
解决方法根据你的系统而不同，可以看这个https://github.com/wkhtmltopdf/wkhtmltopdf/issues/3001。

我的情况靠更新wkhtmltopdf解决的。

希望有所帮助。

@XuDing 谢谢 已从您推荐的地方找到解决办法。

查看是否引用了字体，注释掉引用的字体试一下

我是通过以下两步解决这个问题的。希望有帮助

网上有说是要降低ssl版本，我这里没有尝试这种方式，有两个原因：

1、我发现我的版本并不高

[root@centos bin]# openssl version
OpenSSL 1.0.2k-fips  26 Jan 2017

2、其次就是我导出的时候也没有强制要求https

第一步：尝试了在文件这里 vendor\knplabs\knp-snappy\src\Knp\Snappy\AbstractGenerator.php 修改了下

I also get this issue in windows 10.
then I found this QA
and fixed it by changing in executeCommand function
vendor\knplabs\knp-snappy\src\Knp\Snappy\AbstractGenerator.php
$process->getExitCode()!=1?:0,
return [
            $process->getExitCode,
            $process->getOutput(),
            $process->getErrorOutput(),
        ];

to
return [
            $process->getExitCode()!=1?:0,
            $process->getOutput(),
            $process->getErrorOutput(),
        ];

结果，没多久，又报错了这个错误了。mmmmm

第二步： vendor\knplabs\knp-snappy\src\Knp\Snappy\AbstractGenerator.php 注释掉两行，
并加上 exec($command);

exec($command);
// list($status, $stdout, $stderr) = $this->executeCommand($command);
// $this->checkProcessStatus($status, $stdout, $stderr, $command);

如下图：

I narrowed it down to being a problem with the Symfonys Process Class, used in the executeCommand method of the AbstractGenerator class.
$process = new \Symfony\Component\Process\Process($command, NULL, $this->env);

I solved the problem with a hack, replacing the executeCommand method in generate with directly executing the command:
public function generate($input, $output, array $options = array(), $overwrite = false)
    {
        if (null === $this->binary) {
            throw new \LogicException(
                'You must define a binary prior to conversion.'
            );
        }

        $this->prepareOutput($output, $overwrite);

        $command = $this->getCommand($input, $output, $options);

        /** Workaround for Windows Server 2008 + IIS7 */
        exec($command);
//         list($status, $stdout, $stderr) = $this->executeCommand($command);
//         $this->checkProcessStatus($status, $stdout, $stderr, $command);
        /** Workaround End */

        $this->checkOutput($output, $command);
    }

I wasn't really satisfied with that solution, but it worked the last two months without any problems.

参考：github.com/barryvdh/laravel-snappy...