Verify Email address

VerifyEmail.php

<?php

use RuntimeException;

class VerifyEmail
{
    /**
     * @var string
     */
    protected $email_user = '';

    /**
     * @var string
     */
    protected $email_domain = '';

    /**
     * @var array
     */
    protected $mx_records = [];

    /**
     * @var resource
     */
    protected $fsock = false;

    /**
     * @var int
     */
    protected $port = 25;

    /**
     * @var int
     */
    protected $connection_timeout = 2;

    /**
     * @var int
     */
    protected $stream_timeout = 1;

    /**
     * @var string
     */
    protected $sock_host = 'localhost';

    /**
     * @var bool
     */
    protected $verified = false;

    /**
     * @return bool
     *
     * @throws RuntimeException
     */
    protected function verifyDNS()
    {
        if ($this->email_domain === '') {
            throw new RuntimeException('Parameter `email_domain` is empty.');
        }

        return checkdnsrr($this->email_domain, 'MX');
    }

    /**
     * @return array
     *
     * @throws RuntimeException
     */
    protected function retrieveMX()
    {
        if ($this->email_domain === '') {
            throw new RuntimeException('Parameter `email_domain` is empty.');
        }

        getmxrr($this->email_domain, $hosts, $weights);

        $unique_weights = array_unique($weights);

        if(count($unique_weights) !== count($hosts)) {
            $weights = range(1, count($hosts));
        }

        $mx_records = array_combine($weights, $hosts);

        ksort($mx_records);

        return $mx_records;
    }

    /**
     * @return bool
     *
     * @throws RuntimeException
     */
    protected function createConnection()
    {
        if (count($this->mx_records) === 0) {
            throw new RuntimeException('Parameter `mx_records` is empty.');
        }

        $errno = 0;
        $error = '';

        foreach($this->mx_records as $mx_host) {
            if($this->fsock = @fsockopen($mx_host, $this->port, $errno, $error, $this->connection_timeout)) {
                $this->sock_host = $mx_host;
                stream_set_blocking($this->fsock, 1);

                break;
            }
        }

        if ($this->fsock) {
            return true;
        }

        throw new RuntimeException($error, $errno);
    }

    /**
     * @return void
     */
    protected function closeConnection()
    {
        if ($this->fsock) {
            fclose($this->fsock);
        }
    }

    /**
     * @param string $message
     * @param bool $check
     * @return void
     *
     * @throws RuntimeException
     */
    protected function send($message, $check = false)
    {
        if ($this->fsock) {
            stream_set_timeout($this->fsock, $this->stream_timeout);

            fwrite($this->fsock, $message."\n", strlen($message."\n"));

            $response = null;

            while(true) {
                $buffer = fread($this->fsock, 1024);

                if ($buffer === false) {
                    throw new RuntimeException('Host '.$this->sock_host.' does not responding.');
                }

                $response .= $buffer;

                if ($buffer === '') {
                    break;
                }
            }

            if ($check) {
                $this->verified = (stripos($response, '250') === 0);
            }
        } else {
            throw new RuntimeException('Socket connection not found.');
        }
    }

    /**
     * @param string $email_to
     * @param string $email_from
     * @return bool
     *
     * @throws RuntimeException
     */
    public function check($email_to, $email_from)
    {
        list($this->email_user, $this->email_domain) = explode('@', $email_to);

        if ($this->verifyDNS()) {
            $this->mx_records = $this->retrieveMX();

            if ($this->createConnection()) {
                $this->send('HELO '.$this->sock_host);
                $this->send('MAIL FROM: <'.$email_from.'>', true);
                $this->send('RCPT TO: <'.$email_to.'>', true);
                $this->send('QUIT');

                $this->closeConnection();
            }
        }

        return $this->verified;
    }
}