WordPress: create AJAX calendar

Working on one project, I got an idea to create a custom posts calendar which will be updated by ajax call.

First, I forked get_calendar() function. I copied the function to functions.php file and renamed to get_calendar_local().
I changed the view of the calendar and made it look as following:

Left/right buttons are coded as following:

$calendar_output = '

	
';
    $nonce = wp_create_nonce("calendar_nonce");
      if ($previous)
  		$calendar_output .= "\n\t\t".'
  		year."-".$previous->month) . '" title="' . esc_attr( sprintf(__('View posts for %1$s %2$s'), $wp_locale->get_month($previous->month), date('Y', mktime(0, 0 , 0, $previous->month, 1, $previous->year)))) . '">
  		';
      else
              $calendar_output .= "\n\t\t".'
               ';


    $calendar_output .= "\n\t\t".'
                   '.
        sprintf($calendar_caption, $wp_locale->get_month($thismonth), date('Y', $unixmonth))
    .'';

    if ($next)
      		$calendar_output .= "\n\t\t".'
      		year."-". $next->month) . '" title="' . esc_attr( sprintf(__('View posts for %1$s %2$s'), $wp_locale->get_month($next->month), date('Y', mktime(0, 0 , 0, $next->month, 1, $next->year))) ) . '">'
                  . ' ';
    else
        $calendar_output .= "\n\t\t".'
         ';
    $calendar_output .= '
	
	';

Then I added proper handling for left/right buttons in javascript:

jQuery(function($) {
$("a.calendar").live("click", function() {
          month = $(this).attr("data-month");
          nonce = $(this).attr("data-nonce");
        $(".calendar-data").fadeOut();
          $.ajax({
             type : "post",
             dataType : "json",
             url : myAjax.ajaxurl,
             data : {action: "calendar_action", month : month, nonce: nonce, pll_load_front: true},
             success: function(response) {
                if(response.type == "success") {

                   $("#calendar-content").html(response.content)
                 $(".calendar-data").fadeIn();
                }

             },
              error: function(){
                  $(".calendar-data").fadeIn();
              }
          })
        return false;

       });
});

I use Polylang for multilingual support and I needed to specify language in order to localize ajax request.
The following lines should be added to functions.php actions ‘wp_enqueue_scripts’.

wp_localize_script( 'local', 'myAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php?lang='.pll_current_language("slug") )));
    wp_enqueue_script( 'local' );

The most interesting part – adding ajax function support to functions.php:

add_action("wp_ajax_calendar_action", "calendar_action", 6);

function calendar_action() {
    global $monthnum, $year, $wp_locale;
    if ( !wp_verify_nonce( $_REQUEST['nonce'], "calendar_nonce")) {
          exit("No naughty business please");
       }
    list($year, $monthnum) = explode("-", $_REQUEST['month']);
    $result["type"]="success";
    $result["content"] = get_calendar_local(false, false);
    if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {

          echo json_encode($result);
       }
       else {
          header("Location: ".$_SERVER["HTTP_REFERER"]);
       }
    die();

}