来源：https://www.w3schools.com/tags/att_form_enctype.asp

<form action="/action_page_binary.asp" method="post" enctype="multipart/form-data">
  <label for="fname">First name:</label>
  <input type="text" id="fname" name="fname"><br><br>
  <label for="lname">Last name:</label>
  <input type="text" id="lname" name="lname"><br><br>
  <input type="submit" value="Submit">
</form>

enctype：form 提交时的 header type

Definition and Usage

The enctype attribute specifies how the form-data should be encoded when submitting it to the server.

Note: The enctype attribute can be used only if method="post".

<form enctype="value">

• application/x-www-form-urlencoded - Default. All characters are encoded before sent (spaces are converted to "+" symbols, and special characters are converted to ASCII HEX values)
• multipart/form-data - This value is necessary if the user will upload a file through the form
• text/plain - Sends data without any encoding at all. Not recommended