Simple validation of Czech company ID (IČ).
$ composer require lightools/company-id-validator
$validator = new Lightools\CompanyIdValidator\CompanyIdValidator();
$validator->isValidId('27082440'); // true
$validator->isValidId('25596641'); // true
$validator->isValidId('1859951'); // true (leading zero added, you can disable this function in constructor)
$validator->isValidId('12345678'); // false
If you want to know if subject with some ID really exists, you can use lightools/ares.
$ vendor/bin/tester tests