jQuery Ajax无法正常工作

here's my function:

$(".home .up_0").click(function() {
    $.post("includes/vote.php",   
        {truc : $(this).attr("id")},
        function(data) {
            if(data==1) {
                $(this).parents('.home').find('.score_neutre').append(
                    $(this).parents('.home').find('.score_neutre').val()+1
                );
            } else  {
                alert("Error !");
            }
        },
        "json"
    );
});

When I click everything works but it doesn't change the .score_neutre value (which is 1 and I want it to change to 2).

You need to test (data.score==1) not data

"score" being the associated array name for the json data you sent in.

What does your json response look like? You can't compare it like this with a number.

Additionally you are using append which most likely is wrong. I guess want you really wanted to do is

var ele = $(this).parents('.home').find('.score_neutre');
ele.val(ele.val()+1);