将变量添加到使用jquery发布的数据

I have the following code which is working correctly.I need to assign a variable to the data returned from the php code.Please help me solve this problem because it is really disturbing me

    $(document).ready(function(){
            $('#nickname').keyup(function(){
                $('#checkUser').show();
                var nickname=$(this).val();
                if(nickname !=''){
                    $.post('php/checkUser.php',{nickname:nickname},function(data){
//for example var value=$(this).val(data);
                        if(data=='false'){
                            $('#checkUser').html('<img src="images/true.png" &nbsp width=15>');
                            $('#nickname').css('width','382');
                        } else if(data=='true'){
                            $('#checkUser').html('<img src="images/false.png" &nbsp width=15>');
                            $('#nickname').css('width','382');
                        }
                    });
                }else{
                    $('#nickname').css('width','400');
                    $('#checkUser').hide();
                }
            });
        });

I just saw your live code and debugged it, Found this issue:

Your php script is returning " false" instead of "false" that's why if(data=='false') is not working

if you add your checkUser.php code I can help you further...