wkhtmltopdf generate pdf stream without temporary file

wkhtmltopdf.php

<?php

use Symfony\Component\Process\Process;

class DocumentGenerator
{

  private function wkhtmltopdf(string $html): string
    {
        $wkhtmltopdfProcess = new Process('/usr/bin/wkhtmltopdf -q - -');
        $wkhtmltopdfProcess->setInput($html);
        $wkhtmltopdfProcess->start();
        $exitCode = $wkhtmltopdfProcess->wait();
        if (0 !== $exitCode) {
            throw new DocumentGeneratorException(
                'wkhtmltopdf process error: ' . $wkhtmltopdfProcess->getErrorOutput(),
                $exitCode
            );
        }
    
        if (substr($output, 0, 5) !== '%PDF-') {
            throw new DocumentGeneratorException(
                'wkhtmltopdf return not pdf output: ' . $wkhtmltopdfProcess->getOutput()
            );
        }

        return $wkhtmltopdfProcess->getOutput();
    }
}