get_sans_from_csr.php

<?php

function get_sans_from_csr($csr) {
    $tempFile = tempnam(sys_get_temp_dir(), 'csr');
    file_put_contents($tempFile, $csr);

    $opensslCsrOutput = shell_exec("openssl req -noout -text -in " . escapeshellarg($tempFile));
    unlink($tempFile);

    if ($opensslCsrOutput !== null) {
        $matches = [];
        preg_match('/Subject Alternative Name:\s*(.*)/', $opensslCsrOutput, $matches);

        if (!empty($matches[1])) {
            $sans = [];
            $sanValues = explode(', ', $matches[1]);

            foreach ($sanValues as $value) {
                $san = trim(str_replace(['DNS:', 'IP:'], '', $value));
                $sans[] = $san;
            }

            return $sans;
        }
    }

    return null;
}