WordPress "as blog" function

asBlog.php

<?php

function asBlog($blogId, $function) {
  return function(...$arguments) use($blogId, $function) {
    switch_to_blog($blogId);
    $output = $function(...$arguments);
    restore_current_blog();
    return $output;
  };
}

// For PHP < 5.6:

function asBlog($blogId, $function) {
  return function() use($blogId, $function) {
    switch_to_blog($blogId);
    $output = call_user_func_array($function, func_get_args());
    restore_current_blog();
    return $output;
  };
}