[PHP] 변수에 함수를 넣어서 실행하기

<?
function do_something(){
  echo "done\n";
}
function something_else(){
  echo "we did something else\n";
}
function test_dynamic_functions() {
  $which_function = do_something;
  $which_function();
  $which_function = something_else;
  $which_function();
}

test_dynamic_functions();
?>