Check https certificate

httpsCertificateLookup.php

<?php

/*
MIT license 
Copyright (c) 2022 Mirco Babin
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
*/

$now = new DateTime();
$url = 'https://php.net';

$certificateInfo = httpsCertificateLookup($url);
if ($certificateInfo['https-success']) {
    $interval = $now->diff($certificateInfo['https-certificate-validto']);
    echo $interval->format('%R%a days to expiration');
} else {
    echo 'Error retrieving certificate:'.PHP_EOL;
    echo $certificateInfo['https-error'];
}    


function httpsCertificateLookup(string $url)
{
    $result = [
        'https-success' => false,
        'https-error' => '',
        'https-certificate-data' => null,
        'https-certificate-domain' => null,
        'https-certificate-validfrom' => null,
        'https-certificate-validto' => null,
    ];

    $scheme = null;
    $host = null;
    $port = null;

    $parts = parse_url($url);
    if (false !== $parts) {
        if (isset($parts['scheme'])) {
            $scheme = strtolower($parts['scheme']);
        }
        if (isset($parts['host'])) {
            $host = strtolower($parts['host']);
        }
        if (isset($parts['port'])) {
            $port = intval($parts['port']);
        }
    }

    if (null === $host) {
        $result['https-error'] = 'Could not determine host for: '.$url;

        return $result;
    }

    if (null === $port) {
        if ('http' === $scheme) {
            $port = 80;
        } elseif ('https' === $scheme) {
            $port = 443;
        }

        if (null === $port) {
            $result['https-error'] = 'Could not determine port for: '.$url;

            return $result;
        }
    }

    $context = @stream_context_create(['ssl' => ['capture_peer_cert' => true, 'verify_peer' => false]]);
    $errno = 0;
    $errstr = '';
    $hostAndPort = $host.':'.$port;
    $stream = @stream_socket_client('ssl://'.$hostAndPort, $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $context);
    if (false !== $stream) {
        $context_parms = @stream_context_get_params($stream);
        $certificate = $context_parms['options']['ssl']['peer_certificate'];
        @fclose($stream);

        $result['https-success'] = true;

        $x509_data = @openssl_x509_parse($certificate);
        if (is_array($x509_data)) {
            $result['https-certificate-data'] = $x509_data;

            if (isset($x509_data['subject']['CN'])) {
                $result['https-certificate-domain'] = $x509_data['subject']['CN'];
            }

            if (isset($x509_data['validFrom_time_t'])) {
                $time = new DateTime('@'.$x509_data['validFrom_time_t']);
                $time->setTimezone(new DateTimeZone('UTC'));
                $result['https-certificate-validfrom'] = $time;
            }

            if (isset($x509_data['validTo_time_t'])) {
                $time = new DateTime('@'.$x509_data['validTo_time_t']);
                $time->setTimezone(new DateTimeZone('UTC'));
                $result['https-certificate-validto'] = $time;
            }
        }
    } else {
        $result['https-error'] = 'ssl://'.$hostAndPort.' failed '.$errno.': '.$errstr;
    }

    return $result;
}

On php #externals maillist https://externals.io/message/121040 @bohwaz shared a certificate validation check. See https://gist.github.com/bohwaz/a3e4eb91e82f12768b69f8d24cf0cca8

Because this initiative comes from the php #externals mailinglist, I thought I also share my solution. Because I also have to check certificate expiration dates for websites.

I'm not subscribed to the php #externals mailinglist. So I ping @derickr here. This is about a tool to check the https certificate for https://php.net and possible other sites.