Email validation

<?php

    function validate_email ($email, $fromAddress = '[email protected]', $socketTimeout = 1) {

        // Validate email syntax
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            return FALSE;
        }

        // Extract domain portion of email address
        $parts = explode('@', $email);
        $domain = array_pop($parts);

        // Look up MX for domain
        if (!getmxrr($domain, $mxHosts)) {
            return FALSE;
        }

        // Loop MX hosts until we find one we can connect to
        foreach ($mxHosts as $host) {

            if (ip2long($host) !== FALSE) {
                // $host is already an IP - should never happen but just in case
                $ip = $host;
            } else {
                // Lookup IP for $host
                $ip = gethostbyname($host);
                if ($ip === $host) {
                    continue;
                }
            }

            // Try and connect
            if (!$sock = fsockopen($ip, 25, $errNo, $errStr, $socketTimeout)) {
                continue;
            }

            // Set timeout for read ops
            $secs = floor($socketTimeout);
            $usecs = $socketTimeout - $secs;
            stream_set_timeout($sock, $secs, $usecs);

        }

        // If we haven't made a connection we've failed! Must do better.
        if (!$sock) {
            return FALSE;
        }

        // Have a little chat in SMTP. If any operation fails, consider the email address invalid
        while ($response = fgets($sock)) { // Should be a 220 intro
            if (substr($response, 0, 3) !== '220') {
                return FALSE;
            }
            if (trim($response[3]) === '') {
                break;
            }
        }
        if (!fwrite($sock, "HELO just.visiting\n")) { // Send HELO, should get a 250
            return FALSE;
        }
        while ($response = fgets($sock)) {
            if (substr($response, 0, 3) !== '250') {
                return FALSE;
            }
            if (trim($response[3]) === '') {
                break;
            }
        }
        if (!fwrite($sock, "MAIL FROM: <$fromAddress>\n")) { // MAIL FROM, should get a 250
            return FALSE;
        }
        while ($response = fgets($sock)) {
            if (substr($response, 0, 3) !== '250') {
                return FALSE;
            }
            if (trim($response[3]) === '') {
                break;
            }
        }
        if (!fwrite($sock, "RCPT TO: <$email>\n")) { // RCPT TO, should get a 250 if the address exists
            return FALSE;
        }
        while ($response = fgets($sock)) {
            if (substr($response, 0, 3) !== '250') {
                return FALSE;
            }
            if (trim($response[3]) === '') {
                break;
            }
        }
        fwrite($sock, "QUIT\n");
        fclose($sock);

        // Success!
        return TRUE;

    }