我相信Amin已经回答了您的问题，但我只是想根据

I believe Amin has already answered your question but I just wanted to add that according to the .load() documentation, you can pass your data as the second argument and it should handle the encoding. So you could do something like this:

var pageVal= <?=$_GET['page']?>;
var data = { "topicid": $(this).data('topicid'), "page": pageVal };
$('span.user-topicid').load('get_number_comments.php', data);