Account number without national checksum included

[Vincz]

Hi! When trying to validate a French Iban, for example: FR1420041010050500013M02606
The call to iban_get_parts returns the following:

[
  "checksum" => "14"
  "bban" => "20041010050500013M02606"
  "bank" => "20041"
  "country" => "FR"
  "branch" => "01005"
  "account" => "0500013M02606"
  "nationalchecksum" => "06"
]

The national checksum is included in the account number. Is there a proper way to get these account number without the national checksum, as on website like https://bank.codes/iban/validate/ for example?
I would be tempted to just remove the size of the national checksum from the end of the account number but if it works for France, I'm not sure it would work for others countries.