script to get the expiry date of the SSL cert of a specific domain

checkSSLValidity.php

<?php

date_default_timezone_set('Europe/Luxembourg');

$expiryDate = getCertExpiryDate('mona.lu');

if ($expiryDate) {
    echo date('r', $expiryDate );
}

function getCertExpiryDate($domain) {
    $get = stream_context_create(array("ssl" => array("capture_peer_cert" => TRUE)));
    $read = stream_socket_client("ssl://$domain:443", $errno, $errstr, 30, STREAM_CLIENT_CONNECT, $get);
    $cert = stream_context_get_params($read);
    $certinfo = openssl_x509_parse($cert['options']['ssl']['peer_certificate'], true);

    if (strpos($certinfo['extensions']['subjectAltName'], $domain)) {
        return $certinfo['validTo_time_t'];
    }

    return false;

}