function save($data)
{
    $allData = load();
    array_push($allData, $data);
    global $filePath;
    $fp = fopen($filePath, 'w+') or die("I could not open $filePath.");
    fwrite($fp, serialize($allData));
    echo "{status:"success" , result:" . (string)(count($allData) - 1) . "}";
    fclose($fp);
}

$jQuery.ajax({
            url: serverUrl,
            type: "GET",
            data: {method: "save", data: jQuery.param(pData)},
            cache: false,
            success: function (data) {
                alert("data");
            }
        });

echo '{"status": "success", "result": "'. (string)(count($allData) - 1) .'"}';

alert(data.status);

$jQuery.ajax({
            url: serverUrl,
            type: "GET",
            data: {method: "save", data: jQuery.param(pData)},
            dataType: 'json', //added by me
            cache: false,
            success: function (data) {
                alert("data");
            }
        });

$var  = array('status' => 'success', 'result' => count($allData) - 1 );
echo json_encode($var);