wp_mkdir_p

 public function folders()
 {
     global $mf_domain;
     $dir_list = "";
     $dir_list2 = "";
     wp_mkdir_p(MF_FILES_DIR);
     wp_mkdir_p(MF_CACHE_DIR);
     if (!is_dir(MF_CACHE_DIR)) {
         $dir_list2 .= "<li>" . MF_CACHE_DIR . "</li>";
     } elseif (!is_writable(MF_CACHE_DIR)) {
         $dir_list .= "<li>" . MF_CACHE_DIR . "</li>";
     }
     if (!is_dir(MF_FILES_DIR)) {
         $dir_list2 .= "<li>" . MF_FILES_DIR . "</li>";
     } elseif (!is_writable(MF_FILES_DIR)) {
         $dir_list .= "<li>" . MF_FILES_DIR . "</li>";
     }
     if ($dir_list2 != "") {
         echo "<div id='magic-fields-install-error-message' class='error'><p><strong>" . __('Magic Fields is not ready yet.', $mf_domain) . "</strong> " . __('must create the following folders (and must chmod 777):', $mf_domain) . "</p><ul>";
         echo $dir_list2;
         echo "</ul></div>";
     }
     if ($dir_list != "") {
         echo "<div id='magic-fields-install-error-message-2' class='error'><p><strong>" . __('Magic Fields is not ready yet.', $mf_domain) . "</strong> " . __('The following folders must be writable (usually chmod 777 is neccesary):', $mf_domain) . "</p><ul>";
         echo $dir_list;
         echo "</ul></div>";
     }
 }