Validate domain or email address

validate.php

<?php

/**
 * @param $domain
 * @return mixed
 */
function validateDomain($domain)
{
	$ip = filter_var(gethostbyname($domain), FILTER_VALIDATE_IP);
	// Will return the IP address if or false if the domain is not valid
	return $ip;
}

$emailAddress = '[email protected]';

/**
 * @param $emailAddress
 * @return mixed
 */
function validateEmailAddress($emailAddress)
{
	$validEmail = filter_var($emailAddress, FILTER_VALIDATE_EMAIL);
	// Will return the email address or false if the email is not valid
	return $validEmail;
}

/**
 * @var string $toemail Email address to be checked
 * @var string $fromemail A valid email address to provide the server
 * @var bool   $getdetails Get actual details fo the connection
 *
 * @return ezcConsoleOptionStringNotWellformedException | string 
 * Will return "valid" if the email is valid
 * Will return "invalid" if the email is invalid
 * 
 * Some mail servers will silentlty reject the test message, to prevent 
 * spammers from checking against their users' emails and filter the 
 * valid emails, so this function might not work properly with all mail servers.
 */
function verifyEmail($toemail, $fromemail, $getdetails = false)
{
	$email_arr = explode("@", $toemail);
	$domain = array_slice($email_arr, -1);
	$domain = $domain[0];
	// Trim [ and ] from beginning and end of domain string, respectively
	$domain = ltrim($domain, "[");
	$domain = rtrim($domain, "]");
	if ("IPv6:" == substr($domain, 0, strlen("IPv6:"))) {
		$domain = substr($domain, strlen("IPv6") + 1);
	}
	$mxhosts = array();
	if (filter_var($domain, FILTER_VALIDATE_IP)) {
		$mx_ip = $domain;
	} else {
		getmxrr($domain, $mxhosts, $mxweight);
	}
	if (!empty($mxhosts)) {
		$mx_ip = $mxhosts[array_search(min($mxweight), $mxhosts)];
	} else {
		if (filter_var($domain, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
			$record_a = dns_get_record($domain, DNS_A);
		} elseif (filter_var($domain, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
			$record_a = dns_get_record($domain, DNS_AAAA);
		}
		if (!empty($record_a)) {
			$mx_ip = $record_a[0]['ip'];
		} else {
			$result = "invalid";
			$details .= "No suitable MX records found.";
			return ((true == $getdetails) ? array($result, $details) : $result);
		}
	}

	$connect = @fsockopen($mx_ip, 25);
	if ($connect) {
		if (preg_match("/^220/i", $out = fgets($connect, 1024))) {
			fputs($connect, "HELO $mx_ip\r\n");
			$out = fgets($connect, 1024);
			$details .= $out . "\n";

			fputs($connect, "MAIL FROM: <$fromemail>\r\n");
			$from = fgets($connect, 1024);
			$details .= $from . "\n";
			fputs($connect, "RCPT TO: <$toemail>\r\n");
			$to = fgets($connect, 1024);
			$details .= $to . "\n";
			fputs($connect, "QUIT");
			fclose($connect);
			if (!preg_match("/^250/i", $from) || !preg_match("/^250/i", $to)) {
				$result = "invalid";
			} else {
				$result = "valid";
			}
		}
	} else {
		$result = "invalid";
		$details .= "Could not connect to server";
	}
	if ($getdetails) {
		return array($result, $details);
	} else {
		return $result;
	}
}