File: src/Filter/Special/EmailAddressFilter.php

<?php
declare(strict_types=1);
namespace ParagonIE\Ionizer\Filter\Special;

use ParagonIE\Ionizer\Filter\StringFilter;
use ParagonIE\Ionizer\InvalidDataException;

/**
 * Class EmailAddressFilter
 * @package ParagonIE\Ionizer\Filter\Special
 */
class EmailAddressFilter extends StringFilter
{
    /**
     * @var bool $checkDNS
     */
    protected $checkDNS = true;

    public function __construct()
    {
        $this->addThisCallback('validateEmailAddress');
    }

    /**
     * @param bool $value
     *
     * @return self
     */
    public function setCheckDNS(bool $value): self
    {
        $this->checkDNS = $value;
        return $this;
    }

    /**
     * @param string $input
     *
     * @return string
     * @throws InvalidDataException
     */
    public function validateEmailAddress(string $input): string
    {
        /** @var string|bool $filtered */
        $filtered = \filter_var($input, FILTER_VALIDATE_EMAIL);
        if (!\is_string($filtered)) {
            throw new InvalidDataException('Invalid email address: ' . $input);
        }
        $pos = \strpos($filtered, '@');
        if ($pos === false) {
            throw new InvalidDataException('Invalid email address (no @): ' . $input);
        }
        if (\substr_count($filtered, '@') !== 1) {
            throw new InvalidDataException('Invalid email address (more than one @): ' . $input);
        }
        if ($pos === 0) {
            throw new InvalidDataException('Invalid email address (no username): ' . $input);
        }
        /**
         * @var string $username
         * @var string $domain
         */
        list ($username, $domain) = \explode('@', $filtered);
        if (\preg_match('#^\.#', $username) || \preg_match('#\.$#', $username)) {
            throw new InvalidDataException('Invalid email address (leading or trailing dot): ' . $input);
        }
        if (\strpos($filtered, '..') !== false) {
            throw new InvalidDataException('Invalid email address (consecutive dots): ' . $input);
        }
        if ($this->checkDNS) {
            if (!\preg_match('#^\[?' . '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' . '\]?$#', $domain)) {
                if (!\checkdnsrr($domain, 'MX')) {
                    throw new InvalidDataException('Invalid email address (no MX record on domain): ' . $input);
                }
            }
        }

        return $filtered;
    }
}