root@xxx:~# cat test.php
<?php

var_dump(glob('my_dns_test_folder/*.dns'));
root@xxx:~# ls my_dns_test_folder/
documentation__which_never_exists.md  noideaB.dns  zoneA.dns
root@xxx:~# php test.php
array(2) {
  [0]=>
  string(30) "my_dns_test_folder/noideaB.dns"
  [1]=>
  string(28) "my_dns_test_folder/zoneA.dns"
}