EAN-13 add letters in combinations

[Alexadatasocial]

If it is a normal product, I have modified the Validate.php file and edited leaving it like this
return! $ ean13 || preg_match ('/ ^ [a-zA-Z0-9] {0.13} $ /', $ ean13);
and works.

But when it is a product with combinations I cannot add this EAN with Letters

I need help to validate this and that allows me to add EAN with letters in the combinations.

Thank you