When running from script the function may require ftp_pasv, for swithching server to pasive mode.
If you are behind firewall ftp_mlsd will return FALSE otherwise.(PHP 7 >= 7.2.0, PHP 8)
ftp_mlsd — Devuelve la lista de ficheros de un directorio dado
   Devuelve un array de arrays con la información de los ficheros del directorio especificado
   en caso de éxito o false si hay un error.
  
| Versión | Descripción | 
|---|---|
| 8.1.0 | El parámetro ftpahora espera una instancia de
  FTP\Connection ; anteriormente, se esperaba un resource. | 
Ejemplo #1 Ejemplo con ftp_mlsd()
<?php
// establecimiento de una conexión básica
$ftp = ftp_connect($ftp_server);
// conexión con un nombre de usuario y una contraseña
$login_result = ftp_login($ftp, $ftp_user_name, $ftp_user_pass);
// obtiene el contenido del directorio actual
$contents = ftp_mlsd($ftp, ".");
// muestra $contents
var_dump($contents);
?>Resultado del ejemplo anterior es similar a:
array(5) {
  [0]=>
  array(8) {
    ["name"]=>
    string(1) "."
    ["modify"]=>
    string(14) "20171212154511"
    ["perm"]=>
    string(7) "flcdmpe"
    ["type"]=>
    string(4) "cdir"
    ["unique"]=>
    string(11) "811U5740002"
    ["UNIX.group"]=>
    string(2) "33"
    ["UNIX.mode"]=>
    string(4) "0755"
    ["UNIX.owner"]=>
    string(2) "33"
  }
  [1]=>
  array(8) {
    ["name"]=>
    string(2) ".."
    ["modify"]=>
    string(14) "20171212154511"
    ["perm"]=>
    string(7) "flcdmpe"
    ["type"]=>
    string(4) "pdir"
    ["unique"]=>
    string(11) "811U5740002"
    ["UNIX.group"]=>
    string(2) "33"
    ["UNIX.mode"]=>
    string(4) "0755"
    ["UNIX.owner"]=>
    string(2) "33"
  }
  [2]=>
  array(8) {
    ["name"]=>
    string(11) "public_html"
    ["modify"]=>
    string(14) "20171211171525"
    ["perm"]=>
    string(7) "flcdmpe"
    ["type"]=>
    string(3) "dir"
    ["unique"]=>
    string(11) "811U5740525"
    ["UNIX.group"]=>
    string(2) "33"
    ["UNIX.mode"]=>
    string(4) "0755"
    ["UNIX.owner"]=>
    string(2) "33"
  }
  [3]=>
  array(8) {
    ["name"]=>
    string(10) "public_ftp"
    ["modify"]=>
    string(14) "20171211174536"
    ["perm"]=>
    string(7) "flcdmpe"
    ["type"]=>
    string(3) "dir"
    ["unique"]=>
    string(11) "811U57405EE"
    ["UNIX.group"]=>
    string(2) "33"
    ["UNIX.mode"]=>
    string(4) "0755"
    ["UNIX.owner"]=>
    string(2) "33"
  }
  [4]=>
  array(8) {
    ["name"]=>
    string(3) "www"
    ["modify"]=>
    string(14) "www"
    ["perm"]=>
    string(7) "flcdmpe"
    ["type"]=>
    string(3) "dir"
    ["unique"]=>
    string(11) "811U5740780"
    ["UNIX.group"]=>
    string(2) "33"
    ["UNIX.mode"]=>
    string(4) "0755"
    ["UNIX.owner"]=>
    string(2) "33"
  }
}
When running from script the function may require ftp_pasv, for swithching server to pasive mode.
If you are behind firewall ftp_mlsd will return FALSE otherwise.I have yet to find a resolution to this; but I notice the ftp_mlsd command is limited in the number of files it will grab at once. For me it ranged between 7,500 and 8,500 files. Seems to me there is some max duration it will query for and what you get is a function of how fast the files can be enumerated.sometimes it is necessary to set:
ftp_set_option($this->connection_id, FTP_USEPASVADDRESS, false)
before you set:
ftp_pasv($this->connection_id, $state)