动态依赖多关系下拉使用（Jquery，AJAX，PHP，MySQL）

Question

我还在学习php，但是当我想使用jquery，ajax，php和mysql创建一个4动态依赖下拉列表时，我遇到了这个问题。我能够发现一个有效的代码但是当我尝试编辑jquery代码时它不起作用。难道我做错了什么？。我已经复制了编辑代码和工作代码进行调试。我想创建一个4动态选择框，其中包含以下内容。 Oldgroup，group，district和address。善意的帮助。提前谢谢。

编辑代码 编辑后的代码采用jquery格式。 id是旧组，组，区和地址。

$(document).ready(function() {
//Change in continent dropdown list will trigger this function and
//generate dropdown options for county dropdown
$(document).on('change','#oldgroup', function() {
    var oldgroup_id = $(this).val();
    if(oldgroup_id != "") {
        $.ajax({
            url:"get_data.php",
            type:'POST',
            data:{oldgroup_id:oldgroup_id},
            success:function(response) {
                //var resp = $.trim(response);
                if(response != '') {
                    $("#group").removeAttr('disabled','disabled').html(response);
                    $("#district").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                } else {
                    $("#group, #district, #address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                }
            }
        });
    } else {
        $("#group, #district, #address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
    }
});


//Change in coutry dropdown list will trigger this function and
//generate dropdown options for state dropdown
$(document).on('change','#group', function() {
    var group_id = $(this).val();
    if(group_id != "") {
        $.ajax({
            url:"get_data.php",
            type:'POST',
            data:{group_id:group_id},
            success:function(response) {
                //var resp = $.trim(response);
                if(response != '') $("#district").removeAttr('disabled','disabled').html(response);
                else $("#district, #address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
            }
        });
    } else {
        $("#district, #address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
    }
});



//Change in state dropdown list will trigger this function and
//generate dropdown options for city dropdown
$(document).on('change','#district', function() {
    var district_id = $(this).val();
    if(district_id != "") {
        $.ajax({
            url:"get_data.php",
            type:'POST',
            data:{district_id:district_id},
            success:function(response) {
                if(response != '') $("#address").removeAttr('disabled','disabled').html(response);
                else $("#address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
            }
        });
    } else {
        $("#address").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
    }
});

工作代码 - 这是具有 - 大陆，国家，州和城市的工作代码我想创建一个4动态选择框，其中包含以下内容。 Oldgroup，group，district和address。善意的帮助。提前谢谢。

 $(document).ready(function() 
            //Change in continent dropdown list will trigger this function and
            //generate dropdown options for county dropdown
            $(document).on('change','#continent', function() {
                var continent_id = $(this).val();
                if(continent_id != "") {
                    $.ajax({
                        url:"get_data.php",
                        type:'POST',
                        data:{continent_id:continent_id},
                        success:function(response) {
                            //var resp = $.trim(response);
                            if(response != '') {
                                $("#country").removeAttr('disabled','disabled').html(response);
                                $("#state").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                            } else {
                                $("#country, #state, #city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                            }
                        }
                    });
                } else {
                    $("#country, #state, #city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                }
            });


            //Change in coutry dropdown list will trigger this function and
            //generate dropdown options for state dropdown
            $(document).on('change','#country', function() {
                var country_id = $(this).val();
                if(country_id != "") {
                    $.ajax({
                        url:"get_data.php",
                        type:'POST',
                        data:{country_id:country_id},
                        success:function(response) {
                            //var resp = $.trim(response);
                            if(response != '') $("#state").removeAttr('disabled','disabled').html(response);
                            else $("#state, #city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                        }
                    });
                } else {
                    $("#state, #city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                }
            });



            //Change in state dropdown list will trigger this function and
            //generate dropdown options for city dropdown
            $(document).on('change','#state', function() {
                var state_id = $(this).val();
                if(state_id != "") {
                    $.ajax({
                        url:"get_data.php",
                        type:'POST',
                        data:{state_id:state_id},
                        success:function(response) {
                            if(response != '') $("#city").removeAttr('disabled','disabled').html(response);
                            else $("#city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                        }
                    });
                } else {
                    $("#city").attr('disabled','disabled').html("<option value=''>------- Select --------</option>");
                }
            });


        });