显然，您不允许在< div> ，无需关闭标签前的表单。我在< div class =modal-body> 之前放置了< form> 标签，解决了我的问题>

Apparently you are not allowed to start a form within a <div> without closing the form before the tag. I solved my problem by placing the <form> tag before <div class="modal-body">