Listing 4. Length Tests for Local Part and Domain

$localLen = strlen($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;
}