当我试图在表单中添加新元素时，Symfony2表单在提交时无效

我在表单中添加了一个按钮Add部分。当用户单击该按钮时，会打开一个提示窗口。提示窗口询问section id之后，它调用ajax从数据库中获取section数据，并创建具有相应字段的section表单。然后我将该子表单（即section表单）附加到现有表单中。但当我提交表单时，symfony会抛出错误，即表单无效。因此，基本上symfony表单不接受附加在现有表单上的新创建的子表单

这就是我在symfony控制器中添加按钮的方式

 $formBuilder-> add('new_sections','hidden',array())
  ->add('add','button', array(
        'label' => 'Add Section',
    ))

在trick文件中，Jquery正在将新字段附加到按钮上的现有表单上单击

 $('#form_add').click(
        function(){
            var section_id = prompt("Please enter your Section ID");
            console.log(section_id);
            $.ajax({url: url, success: function(result){
                var new_section_form ='' +
                        '<div style="border-style: solid; margin-top: 15px; border-radius: 3px; border-width: 1px; padding: 10px;">'+
                        '<label class="required">'+result['section']['section_id']+'</label>'+
                '<div id="form_'+result['section']['section_id']+'" class="SectionForms">'+
                 '       <div><label for="form_'+result['section']['section_id']+'_weight'+result['section']['section_id']+'">Weight </label><input type="text" id="form_'+result['section']['section_id']+'_weight'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][weight'+result['section']['section_id']+']" value="0"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_label'+result['section']['section_id']+'" class="required">label </label><input type="text" id="form_'+result['section']['section_id']+'_label'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][label'+result['section']['section_id']+']" required="required" value="Text Description v2"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_active'+result['section']['section_id']+'" class="required">Active </label><input type="text" id="form_'+result['section']['section_id']+'_active'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][active'+result['section']['section_id']+']" required="required" value="1"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_link'+result['section']['section_id']+'">Link </label><input type="text" id="form_'+result['section']['section_id']+'_link'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][link'+result['section']['section_id']+']"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_events_max'+result['section']['section_id']+'">events_max </label><input type="text" id="form_'+result['section']['section_id']+'_events_max'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][events_max'+result['section']['section_id']+']"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_events_min'+result['section']['section_id']+'">events_min </label><input type="text" id="form_'+result['section']['section_id']+'_events_min'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][events_min'+result['section']['section_id']+']"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_module'+result['section']['section_id']+'">module</label><input type="text" id="form_'+result['section']['section_id']+'_module'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][module'+result['section']['section_id']+']"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_module_icon'+result['section']['section_id']+'">module_icon </label><input type="text" id="form_'+result['section']['section_id']+'_module_icon'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][module_icon'+result['section']['section_id']+']" value="icon_generic"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_module_id'+result['section']['section_id']+'">module_id </label><input type="text" id="form_'+result['section']['section_id']+'_module_id'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][module_id'+result['section']['section_id']+']"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_apicall'+result['section']['section_id']+'">apicall </label><input type="text" id="form_'+result['section']['section_id']+'_apicall'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][apicall'+result['section']['section_id']+']" value="1"></div>'+
                '<div><label for="form_'+result['section']['section_id']+'_template_static'+result['section']['section_id']+'">template_static </label><input type="text" id="form_'+result['section']['section_id']+'_template_static'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][template_static'+result['section']['section_id']+']"></div>'+
                '<input type="hidden" id="form_'+result['section']['section_id']+'_changed'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][changed'+result['section']['section_id']+']" class="changedField" value="2">'+
                 '       <div><button type="button" id="form_'+result['section']['section_id']+'_delete_'+result['section']['section_id']+'" name="form['+result['section']['section_id']+'][delete_'+result['section']['section_id']+']" class="btn-delete">Delete Section No. '+result['section']['section_id']+'</button></div>'+
                '</div>'+
                '</div>'

                $('.SectionForms').last().parent().after(new_section_form);
                $('#form_new_sections').val($('#form_new_sections').val()+" "+result['section']['section_id']);
            }});
        });

但当我提交表格时，它没有进入表格有效块

 if ('POST' === $request->getMethod()) {
        $form->handleRequest($request);
        if ($form->isValid()) {
        // not entering in this block
        }
        }