Sometimes I'm getting fatturas that openssl cant convert because after the header are missing the BOM characters (). I don't know if this is a mistake on my side but nevertheless, if someone is facing the same issue this patch should accept this fatturas as well. This code is a patch of filippotoso/p7m-extractor.

P7M.php

<?php

namespace FilippoToso\P7MExtractor;

use FilippoToso\P7MExtractor\Exceptions\FileNotWritable;
use FilippoToso\P7MExtractor\Exceptions\CouldNotExtractFile;
use FilippoToso\P7MExtractor\Exceptions\P7MNotFound;
use Symfony\Component\Process\Process;

class P7M
{
    protected $source;
    protected $sourceWithBOM;
    protected $destination;
    protected $binPath;

    public function __construct(string $binPath = null)
    {
        $this->binPath = $binPath ?? '/usr/bin/openssl';
    }

    public function setSource(string $source) : self
    {
        $this->checkSource($source);
        $this->source = $source;

        return $this;
    }

    protected function checkSource(string $source)
    {
        if (!is_readable($source)) {
            throw new P7MNotFound(sprintf('Could not find or read p7m `%s`', $source));
        }
    }

    protected function checkBOM(string &$source)
    {
        $data = file_get_contents($source);
        // check if BOM characters are present after the header
        if(strpos(chr(239) . chr(187) . chr(191),$data))
            file_put_contents("temp.xml.p7m",$data);
        else
        {
            //insert BOM characters after header
            $data = explode("<?xml",$data);
            $header = $data[0].chr(239) . chr(187) . chr(191);
            $body = "<?xml".$data[1];
            file_put_contents("temp.xml.p7m",$header.$body);
        }
        $this->sourceWithBOM = "temp.xml.p7m";
    }


    public function setDestination(string $destination) : self
    {
        $this->checkDestination($destination);

        $this->destination = $destination;

        return $this;
    }

    protected function checkDestination(string $destination)
    {
        if (file_exists($destination) && !is_writable($destination)) {
            throw new FileNotWritable(sprintf('Could not wrtie file `%s`', $destination));
        }
    }

    public function save()
    {

        $this->checkSource($this->source);
        $this->checkBOM($source);

        $this->checkDestination($this->destination);

        $process = $this->getProcess();
        $process->run();
        unlink($this->sourceWithBOM);
        if (!$process->isSuccessful()) {
            throw new CouldNotExtractFile($process);
        }

        return true;

    }

    protected function getProcess() {
        $options = [$this->binPath, 'smime', '-verify', '-noverify', '-binary', '-in', $this->sourceWithBOM, '-inform', 'DER', '-out', $this->destination];
        return new Process($options);
    }

    public function get() {

        $this->checkSource($this->source);
        $this->checkBOM($source);

        $originalDestination = $this->destination;
        $this->destination = $this->getTemporaryFile();

        $process = $this->getProcess();
        $process->run();
        unlink($this->sourceWithBOM);
        if (!$process->isSuccessful()) {
            throw new CouldNotExtractFile($process);
        }

        $content = file_get_contents($this->destination);

        $this->destination = $originalDestination;

        return $content;

    }

    protected function getTemporaryFile() {
        $tempDir = rtrim(sys_get_temp_dir(), DIRECTORY_SEPARATOR);
        return tempnam($tempDir, 'p7m');
    }

    public static function convert(string $source, string $destination, string $binPath = null)
    {
        return (new static($binPath))
            ->setSource($source)
            ->setDestination($destination)
            ->save()
        ;
    }

    public static function extract(string $source, string $binPath = null)
    {
        return (new static($binPath))
            ->setSource($source)
            ->get()
        ;
    }

}