check ssl for a given domain

check-ssl.php

<?php

 function checkSsl($domain, $daysThreshold = 7)
    {
        $port = 443; // Default port for HTTPS
        $timeout = 5; // Timeout for the connection

        // Open a connection to the domain
        $context = stream_context_create([
            "ssl" => [
                "capture_peer_cert" => true
            ]
        ]);

        $client = @stream_socket_client(
            "ssl://$domain:$port",
            $errno,
            $errstr,
            $timeout,
            STREAM_CLIENT_CONNECT,
            $context
        );

        if (!$client) {
            return "Error connecting to $domain: $errstr";
        }

        // Get the certificate
        $params = stream_context_get_params($client);
        $cert = openssl_x509_parse($params['options']['ssl']['peer_certificate']);

        if (!$cert) {
            return "Unable to parse SSL certificate for $domain.";
        }

        $validToTimestamp = $cert['validTo_time_t'];
        $daysToExpiration = ($validToTimestamp - time()) / (60 * 60 * 24);

        if ($daysToExpiration <= $daysThreshold) {
            return "the domain $domain is expiring soon";
        }

        return null;
    }