Regex for validating Canada postal code and US zip code

// checks postal code format L4X-1S9
$regex = '/[a-z][0-9][a-z][- ]?[0-9][a-z][0-9]$/i';
if( preg_match($regex, $zip) )
  echo "Valid postal code";


// checks for 5 digit or 9 digit zip code or 12345-6789
// or 123456789
$regex = '/(^\d{5}$)|(^\d{5}-\d{4}$)|(^\d{9}$)/'
if( preg_match($regex, $zip) )
  echo "Valid Zip code";