Product.php
'reference' => array('type' => self::TYPE_STRING, 'validate' => 'isReference', 'size' => 32),
Validate.php
/*
* Check for product reference validity
*
* @param string $reference Product reference to validate
* @return boolean Validity is ok or not
*/
public static function isReference($reference)
{
return preg_match('/^[^<>;={}]*$/u', $reference);
}