Email validator

<?php

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)
        {
            // local part length exceeded
            $isValid = false;
        }
        else if ($domainLen < 1 || $domainLen > 255)
        {
            // domain part length exceeded
            $isValid = false;
        }
        else if ($local[0] == '.' || $local[$localLen-1] == '.')
        {
            // local part starts or ends with '.'
            $isValid = false;
        }
        else if (preg_match('/\\.\\./', $local))
        {
            // local part has two consecutive dots
            $isValid = false;
        }
        else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain))
        {
            // character not valid in domain part
            $isValid = false;
        }
        else if (preg_match('/\\.\\./', $domain))
        {
            // domain part has two consecutive dots
            $isValid = false;
        }
        else if(!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/', str_replace("\\\\","",$local)))
        {

            // character not valid in local part unless
            // local part is quoted
            if (!preg_match('/^"(\\\\"|[^"])+"$/',
            str_replace("\\\\","",$local)))
            {
                $isValid = false;
            }

        }
        if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A")))
        {
            // domain not found in DNS
            $isValid = false;
        }

    }

    return $isValid;

}
?>