Make ssl bundle from domain certificate

get_ssl_bundle.php

#!/usr/bin/env php
<?php
/**
 * Usage: php ./get_ssl_bundle.php example.com.crt
 * 
 * @param string $crtFile
 * @return string
 */
function get_ssl_bundle($crtFile)
{
    $certificates = explode('BEGIN', $crtFile);
    if (count($certificates) > 2) {
        return $crtFile;
    }

    $crtChain[] = $crtFile;
    do {
        $certData = openssl_x509_parse($crtFile);
        if (!isset($certData['extensions']['authorityInfoAccess'])) {
            break;
        }
        $authorityInfoAccess = $certData['extensions']['authorityInfoAccess'];
        preg_match(
            '/https?\:\/\/[^\" ]+\.crt/im',
            $authorityInfoAccess,
            $matches
        );
        $intermediaryUrl = isset($matches[0]) ? $matches[0] : null;
        if (!empty($intermediaryUrl) &&
            filter_var($intermediaryUrl, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED) !== false &&
            $crtFileContent = @file_get_contents($intermediaryUrl)
        ) {
            $intermediaryCrt = chunk_split(base64_encode($crtFileContent), 64, PHP_EOL);
            $crtFile = '-----BEGIN CERTIFICATE-----'.PHP_EOL.$intermediaryCrt.'-----END CERTIFICATE-----';
            $crtChain[] = $crtFile;
        }

    } while (!is_null($intermediaryUrl));

    return implode(PHP_EOL, $crtChain);
}

if (!file_exists($argv[1])) {
    echo "File not found: '{$argv[1]}'" . PHP_EOL;
    exit(1);
}
echo get_ssl_bundle(file_get_contents($argv[1]));
echo PHP_EOL;