js如何调用php函数

jQuery.ajax({
    type: "POST",
    url: 'your_functions_address.php',
    dataType: 'json',
    data: {functionname: 'add', arguments: [1, 2]},
    success: function (obj, textstatus) {
                  if( !('error' in obj) ) {
                      yourVariable = obj.result;
                  }
                  else {
                      console.log(obj.error);
                  }
            }});

 <?php
    header(&#39;Content-Type: application/json&#39;);

    $aResult = array();

    if( !isset($_POST[&#39;functionname&#39;]) ) { $aResult[&#39;error&#39;] = &#39;No function name!&#39;; }

    if( !isset($_POST[&#39;arguments&#39;]) ) { $aResult[&#39;error&#39;] = &#39;No function arguments!&#39;; }

    if( !isset($aResult[&#39;error&#39;]) ) {

        switch($_POST[&#39;functionname&#39;]) {
            case &#39;add&#39;:
               if( !is_array($_POST[&#39;arguments&#39;]) || (count($_POST[&#39;arguments&#39;]) < 2) ) {
                   $aResult[&#39;error&#39;] = &#39;Error in arguments!&#39;;
               }
               else {
                   $aResult[&#39;result&#39;] = add(floatval($_POST[&#39;arguments&#39;][0]), floatval($_POST[&#39;arguments&#39;][1]));
               }
               break;

            default:
               $aResult[&#39;error&#39;] = &#39;Not found function &#39;.$_POST[&#39;functionname&#39;].&#39;!&#39;;
               break;
        }

    }

    echo json_encode($aResult);?>