Check if certificate expiry is in more than 30 days

cert_expiry_check.php

<?php

$domain = 'mydomain.tld';

if (get_ssl_certificate_expiry($domain) < 30) {
	throw new \Exception('Certificate expires in less than 30 days!');
}

function get_ssl_certificate_expiry(string $domain): ?int
{
	$get = stream_context_create(array("ssl" => array("capture_peer_cert" => TRUE)));
	$read = stream_socket_client(sprintf("ssl://%s:443", $domain), $errno, $errstr, 5, STREAM_CLIENT_CONNECT, $get);
	$cert = stream_context_get_params($read);

	if (!isset($cert['options']['ssl']['peer_certificate'])) {
		return 0;
	}

	$certinfo = openssl_x509_parse($cert['options']['ssl']['peer_certificate']);
	$date = $certinfo['validTo_time_t'] ?? null;

	if (!$date) {
		return 0;
	}

	return intval(($date - time()) / 3600 / 24);
}

Absolutely, thanks @CViniciusSDias :) I just typed this code quickly for this gist as the function is part of a larger script :)

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.

https://gist.github.com/MircoBabin/5c420c277b5a039df76c0469ed04c491