Nothing.
string(0) ""
array(16) {
  [0]=>
  string(1) "."
  [1]=>
  string(2) ".."
  [2]=>
  string(9) "alt-php44"
  [3]=>
  string(9) "alt-php51"
  [4]=>
  string(9) "alt-php52"
  [5]=>
  string(9) "alt-php53"
  [6]=>
  string(9) "alt-php54"
  [7]=>
  string(9) "alt-php55"
  [8]=>
  string(9) "alt-php56"
  [9]=>
  string(9) "alt-php70"
  [10]=>
  string(9) "alt-php71"
  [11]=>
  string(9) "alt-php72"
  [12]=>
  string(9) "alt-php73"
  [13]=>
  string(9) "alt-php74"
  [14]=>
  string(9) "alt-php80"
  [15]=>
  string(9) "alt-php81"
}