check for E-Mail

checkEmail.php

<?php

/**
 * checkEmail
 *
 * @param String  $email
 * @param Boolean $mxCheck   (do not use, if you don't need it)
 *
 * @return Boolean
 */
function checkEmail($email, $mxCheck = false)
{
  if (!is_string($email) || strlen($email) >= 320) {
    $valid = false;
  } elseif (!preg_match('/^(.*<?)(.*)@(.*)(>?)$/', $email, $matches)) {
    $valid = false;
  } else {
    $domain = $matches[3];

    if (function_exists('idn_to_ascii')) {
      $email = $matches[1] . $matches[2] . '@' . idn_to_ascii($domain) . $matches[4];
    } else {
      $email = $matches[1] . $matches[2] . '@' . $domain . $matches[4];
    }

    if (!$domain || !$email) {
      $valid = false;
    } else {

      if (function_exists('filter_var') && function_exists('idn_to_ascii')) {

        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
          $valid = false;
        } else {
          $valid = true;
        }

      } else {

        if (function_exists('idn_to_ascii')) {
          $regEx = "/^([\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+\.)*[\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+@((((([a-z0-9]{1}[a-z0-9\-]{0,62}[a-z0-9]{1})|[a-z])\.)+[a-z]{2,6})|(\d{1,3}\.){3}\d{1,3}(\:\d{1,5})?)$/i";
        } else {
          $regEx = "/^([\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+\.)*[\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+@((((([öäüa-z0-9]{1}[öäüa-z0-9\-]{0,62}[öäüa-z0-9]{1})|[öäüa-z])\.)+[öäüa-z]{2,6})|(\d{1,3}\.){3}\d{1,3}(\:\d{1,5})?)$/i";
        }

        if (!preg_match($regEx, $email)) {
          $valid = false;
        } else {
          $valid = true;
        }

      }

      if ($valid && $mxCheck && function_exists('checkdnsrr')) {
        $valid = checkdnsrr($domain . '.', 'MX') || checkdnsrr($domain, 'A');
      }

    }
  }

  return $valid;
}