<?php
  function ValidateEmail($email)
  {
      if(strlen($email) > 78)
        return array("Email address must be below 78 characters");

      // First, we check that there's one @ symbol, and that the lengths are right
      if (!preg_match("/^[^@]{1,64}@[^@]{1,255}$/", $email)) {
          // Email invalid because wrong number of characters in one section, or wrong number of @ symbols.
          return array("Invalid email address");
      }
      // Split it into sections to make life easier
      $email_array = explode("@", $email);
      $local_array = explode(".", $email_array[0]);
      for ($i = 0; $i < sizeof($local_array); $i++) {
          if (!preg_match("/^(([A-Za-z0-9!#$%&'*+\/=?^_`{|}~-][A-Za-z0-9!#$%&'*+\/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$/", $local_array[$i])) {
              return array("Invalid email address");
          }
      }
      if (!preg_match("/^\[?[0-9\.]+\]?$/", $email_array[1])) { // Check if domain is IP. If not, it should be valid domain name
          $domain_array = explode(".", $email_array[1]);
          if (sizeof($domain_array) < 2) {
              return array("Invalid email address"); // Not enough parts to domain
          }
          for ($i = 0; $i < sizeof($domain_array); $i++) {
              if (!preg_match("/^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$/", $domain_array[$i])) {
                  return array("Invalid email address");
              }
          }
      }

      return true;
  }