Upload files asynchronously (AJAX) with HTTP/1.1 PUT method, why not? - ajax

Question

Uploading files via PUT method, even binary or text, via a "normal web browser" is possible.
Why many people are just saying, that is not possible ?
Sample code with jQuery and PHP.
$(document).ready(function() {
$("#uploadbutton").click(function() {
var filename = $("#file").val();
$.ajax({
type: "PUT",
url: "addFile.do",
enctype: 'multipart/form-data',
data: {file: filename},
success: function(){
alert( "Data Uploaded: ");
}
});
});
});
On the server side just read the STDIN stream like
<?php
/* PUT data comes in on the stdin stream */
$putdata = fopen("php://input", "r");
/* Open a file for writing */
$fp = fopen("myputfile.ext", "w");
/* Read the data 1 KB at a time
and write to the file */
while ($data = fread($putdata, 1024))
fwrite($fp, $data);
/* Close the streams */
fclose($fp);
fclose($putdata);
?>

Answer 1

{file: filename}
When you upload a file, you have to upload the file. Telling the server what the local filename is… isn't enough.
JavaScript, running in a web browser in a standard security context, doesn't have access to read the data in the file from the user's hard disk.
Since you can't get the data, you can't upload it.

Answer 2

For your solution specifically, mainly because the PUT method (verb) is not supported by all browsers, especially older ones, so this solution won't work for everyone.
The topic has come up previously as well, though not exactly the same, some answers are examples of where PUT and DELETE don't work.
The documentation for $.ajax() mentions this as well:
type
Default: 'GET'
The type of request to make ("POST" or "GET"), default is "GET".
Note: Other HTTP request methods, such as PUT and DELETE, can also be used here, but they are not supported by all browsers.