属性默认的值为: application/x-www-form-urlencoded

<form action="register" method="post" enctype="application/x-www-form-urlencoded">

不添加enctype属性默认值,上传文件时只会传送文件名字

  <form action="register" method="post" enctype="multipart/form-data">

更改之后才会上传文件本体

学习视频:
https://www.bilibili.com/video/BV1Jq4y1u7im/?spm_id_from=333.337.search-card.all.click&vd_source=3c8c35a76bf8f011c75d2584ec4a3fda