javascript - Use native js to submit images to the server, but the data cannot be received? (See description for details of code and screenshots)

After capturing the packet, I saw an image like this, with more names such as these
Content-Disposition: form-data; Content-Type: image/jpeg

Backend code

<code>$get = $_POST;
file_put_contents("./Upload/img/".time()."-avatar.txt",base64_decode($get));</code>

As a result, this txt is empty

Reply content:

After capturing the packet, I saw an image like this, with more names such as these
Content-Disposition: form-data; Content-Type: image/jpeg

Backend code

<code>$get = $_POST;
file_put_contents("./Upload/img/".time()."-avatar.txt",base64_decode($get));</code>

As a result, this txt is empty