toPem example

if (str_contains($host, ':')) {
            $host = '['.$host.']';
        }

        $this->info['primary_ip'] = $host;
        $this->info['primary_port'] = $stream->getRemoteAddress()->getPort();
        $this->info['pretransfer_time'] = microtime(true) - $this->info['start_time'];
        $this->info['debug'] .= sprintf("* Connected to %s (%s) port %d\n", $request->getUri()->getHost(), $host, $this->info['primary_port']);

        if ((isset($this->info['peer_certificate_chain']) || $this->pinSha256) && null !== $tlsInfo = $stream->getTlsInfo()) {
            foreach ($tlsInfo->getPeerCertificates() as $cert) {
                $this->info['peer_certificate_chain'][] = openssl_x509_read($cert->toPem());
            }

            if ($this->pinSha256) {
                $pin = openssl_pkey_get_public($this->info['peer_certificate_chain'][0]);
                $pin = openssl_pkey_get_details($pin)['key'];
                $pin = \array_slice(explode("\n", $pin), 1, -2);
                $pin = base64_decode(implode('', $pin));
                $pin = base64_encode(hash('sha256', $pin, true));

                if (!\in_array($pin, $this->pinSha256, true)) {
                    throw new TransportException(sprintf('SSL public key does not match pinned public key for "%s".', $this->info['url']));
                }