drupal - How to validate PAN No and Bank account number using php? -

i need validate pan number , bank account number fields. how can using php? have implement validation in civicrm custom form. civicrm has built in function these 2 validations.

pan number validation regular expression

if (!preg_match("/^([a-za-z]){5}([0-9]){4}([a-za-z]){1}?$/", $pannumber)) {   echo "invalid pan number"; }