Email validation function with dns check in php15.09.15

function validEmail($email)
{
   $isValid = true;
   $atIndex = strrpos($email, "@");
   if (is_bool($atIndex) && !$atIndex):
     $isValid = false;
   else:
      $domain = substr($email, $atIndex+1);
      $local = substr($email, 0, $atIndex);
      $localLen = strlen($local);
      $domainLen = strlen($domain);
      if ($localLen < 1 || $localLen > 64):
         $isValid = false;
      elseif($domainLen < 1 || $domainLen > 255):
         $isValid = false;
      elseif($local[0] == '.' || $local[$localLen-1] == '.'):
         $isValid = false;
      elseif(preg_match('/\\.\\./', $local)):
         $isValid = false;
      elseif(!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain)):
         $isValid = false;
      elseif(preg_match('/\\.\\./', $domain)):
         $isValid = false;
      elseif(!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/',str_replace("\\\\","",$local))):
         if (!preg_match('/^"(\\\\"|[^"])+"$/',str_replace("\\\\","",$local))):
           $isValid = false;
       	 endif;
      endif;
      if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A"))):
        $isValid = false;
      endif;
   endif;
   return $isValid;
}

http://www.linuxjournal.com/article/9585?page=0,3

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Email validation function with dns check in php15.09.15

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