PHPMailer::validateAddress PHP Method

    public static function validateAddress($address, $patternselect = null)
    {
        if (is_null($patternselect)) {
            $patternselect = self::$validator;
        }
        if (is_callable($patternselect)) {
            return call_user_func($patternselect, $address);
        }
        //Reject line breaks in addresses; it's valid RFC5322, but not RFC5321
        if (strpos($address, "\n") !== false or strpos($address, "\r") !== false) {
            return false;
        }
        if (!$patternselect or $patternselect == 'auto') {
            //Check this constant first so it works when extension_loaded() is disabled by safe mode
            //Constant was added in PHP 5.2.4
            if (defined('PCRE_VERSION')) {
                //This pattern can get stuck in a recursive loop in PCRE <= 8.0.2
                if (version_compare(PCRE_VERSION, '8.0.3') >= 0) {
                    $patternselect = 'pcre8';
                } else {
                    $patternselect = 'pcre';
                }
            } elseif (function_exists('extension_loaded') and extension_loaded('pcre')) {
                //Fall back to older PCRE
                $patternselect = 'pcre';
            } else {
                //Filter_var appeared in PHP 5.2.0 and does not require the PCRE extension
                if (version_compare(PHP_VERSION, '5.2.0') >= 0) {
                    $patternselect = 'php';
                } else {
                    $patternselect = 'noregex';
                }
            }
        }
        switch ($patternselect) {
            case 'pcre8':
                /**
                 * Uses the same RFC5322 regex on which FILTER_VALIDATE_EMAIL is based, but allows dotless domains.
                 * @link http://squiloople.com/2009/12/20/email-address-validation/
                 * @copyright 2009-2010 Michael Rushton
                 * Feel free to use and redistribute this code. But please keep this copyright notice.
                 */
                return (bool) preg_match('/^(?!(?>(?1)"?(?>\\\\[ -~]|[^"])"?(?1)){255,})(?!(?>(?1)"?(?>\\\\[ -~]|[^"])"?(?1)){65,}@)' . '((?>(?>(?>((?>(?>(?>\\x0D\\x0A)?[\\t ])+|(?>[\\t ]*\\x0D\\x0A)?[\\t ]+)?)(\\((?>(?2)' . '(?>[\\x01-\\x08\\x0B\\x0C\\x0E-\'*-\\[\\]-\\x7F]|\\\\[\\x00-\\x7F]|(?3)))*(?2)\\)))+(?2))|(?2))?)' . '([!#-\'*+\\/-9=?^-~-]+|"(?>(?2)(?>[\\x01-\\x08\\x0B\\x0C\\x0E-!#-\\[\\]-\\x7F]|\\\\[\\x00-\\x7F]))*' . '(?2)")(?>(?1)\\.(?1)(?4))*(?1)@(?!(?1)[a-z0-9-]{64,})(?1)(?>([a-z0-9](?>[a-z0-9-]*[a-z0-9])?)' . '(?>(?1)\\.(?!(?1)[a-z0-9-]{64,})(?1)(?5)){0,126}|\\[(?:(?>IPv6:(?>([a-f0-9]{1,4})(?>:(?6)){7}' . '|(?!(?:.*[a-f0-9][:\\]]){8,})((?6)(?>:(?6)){0,6})?::(?7)?))|(?>(?>IPv6:(?>(?6)(?>:(?6)){5}:' . '|(?!(?:.*[a-f0-9]:){6,})(?8)?::(?>((?6)(?>:(?6)){0,4}):)?))?(25[0-5]|2[0-4][0-9]|1[0-9]{2}' . '|[1-9]?[0-9])(?>\\.(?9)){3}))\\])(?1)$/isD', $address);
            case 'pcre':
                //An older regex that doesn't need a recent PCRE
                return (bool) preg_match('/^(?!(?>"?(?>\\\\[ -~]|[^"])"?){255,})(?!(?>"?(?>\\\\[ -~]|[^"])"?){65,}@)(?>' . '[!#-\'*+\\/-9=?^-~-]+|"(?>(?>[\\x01-\\x08\\x0B\\x0C\\x0E-!#-\\[\\]-\\x7F]|\\\\[\\x00-\\xFF]))*")' . '(?>\\.(?>[!#-\'*+\\/-9=?^-~-]+|"(?>(?>[\\x01-\\x08\\x0B\\x0C\\x0E-!#-\\[\\]-\\x7F]|\\\\[\\x00-\\xFF]))*"))*' . '@(?>(?![a-z0-9-]{64,})(?>[a-z0-9](?>[a-z0-9-]*[a-z0-9])?)(?>\\.(?![a-z0-9-]{64,})' . '(?>[a-z0-9](?>[a-z0-9-]*[a-z0-9])?)){0,126}|\\[(?:(?>IPv6:(?>(?>[a-f0-9]{1,4})(?>:' . '[a-f0-9]{1,4}){7}|(?!(?:.*[a-f0-9][:\\]]){8,})(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,6})?' . '::(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,6})?))|(?>(?>IPv6:(?>[a-f0-9]{1,4}(?>:' . '[a-f0-9]{1,4}){5}:|(?!(?:.*[a-f0-9]:){6,})(?>[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,4})?' . '::(?>(?:[a-f0-9]{1,4}(?>:[a-f0-9]{1,4}){0,4}):)?))?(?>25[0-5]|2[0-4][0-9]|1[0-9]{2}' . '|[1-9]?[0-9])(?>\\.(?>25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])){3}))\\])$/isD', $address);
            case 'html5':
                /**
                 * This is the pattern used in the HTML5 spec for validation of 'email' type form input elements.
                 * @link http://www.whatwg.org/specs/web-apps/current-work/#e-mail-state-(type=email)
                 */
                return (bool) preg_match('/^[a-zA-Z0-9.!#$%&\'*+\\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}' . '[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/sD', $address);
            case 'noregex':
                //No PCRE! Do something _very_ approximate!
                //Check the address is 3 chars or longer and contains an @ that's not the first or last char
                return strlen($address) >= 3 and strpos($address, '@') >= 1 and strpos($address, '@') != strlen($address) - 1;
            case 'php':
            default:
                return (bool) filter_var($address, FILTER_VALIDATE_EMAIL);
        }
    }

 public function verify_emails($emails)
 {
     $invalid_emails_count = 0;
     $exists = 0;
     require_once 'PHPMailer-master/class.phpmailer.php';
     $emails = self::emails_to_array($emails);
     $count_emails = count($emails);
     for ($i = 0; $i < $count_emails; $i++) {
         if (!PHPMailer::validateAddress($emails[$i])) {
             $invalid_emails_count++;
             unset($emails[$i]);
         }
     }
     for ($i = 0; $i < $count_emails; $i++) {
         $exists_in = $this->_db->prepare("SELECT COUNT(*) FROM emails WHERE email = '{$emails[$i]}'");
         $result = $exists_in->execute();
         $exists_in = $exists_in->fetchALL(PDO::FETCH_ASSOC);
         $exists_in = implode('', $exists_in[0]);
         if ($exists_in > 0) {
             $exists++;
             unset($emails[$i]);
         }
     }
     usort($emails, 'strnatcmp');
     return array($emails, $invalid_emails_count, $count_emails - $invalid_emails_count - $exists, $exists);
 }