Sending multipart/formdata with jQuery.ajax

I've got a problem sending a file to a serverside PHP-script using jQuery's ajax-function. It's possible to get the File-List with $('#fileinput').attr('files') but how is it possible to send this Data to the server? The resulting array ($_POST) on the serverside php-script is 0 (NULL) when using the file-input.

I know it is possible (though I didn't find any jQuery solutions until now, only Prototye code (http://webreflection.blogspot.com/2009/03/safari-4-multiple-upload-with-progress.html)).

This seems to be relatively new, so please do not mention file upload would be impossible via XHR/Ajax, because it's definitely working.

I need the functionality in Safari 5, FF and Chrome would be nice but are not essential.

My code for now is:

$.ajax({
    url: 'php/upload.php',
    data: $('#file').attr('files'),
    cache: false,
    contentType: 'multipart/form-data',
    processData: false,
    type: 'POST',
    success: function(data){
        alert(data);
    }
});

Starting with Safari 5/Firefox 4, it’s easiest to use the FormData class:

var data = new FormData();
jQuery.each(jQuery('#file')[0].files, function(i, file) {
    data.append('file-'+i, file);
});

So now you have a FormData object, ready to be sent along with the XMLHttpRequest.

jQuery.ajax({
    url: 'php/upload.php',
    data: data,
    cache: false,
    contentType: false,
    processData: false,
    method: 'POST',
    type: 'POST', // For jQuery < 1.9
    success: function(data){
        alert(data);
    }
});

It’s imperative that you set the contentType option to false, forcing jQuery not to add a Content-Type header for you, otherwise, the boundary string will be missing from it. Also, you must leave the processData flag set to false, otherwise, jQuery will try to convert your FormData into a string, which will fail.

You may now retrieve the file in PHP using:

$_FILES['file-0']

(There is only one file, file-0, unless you specified the multiple attribute on your file input, in which case, the numbers will increment with each file.)

Using the FormData emulation for older browsers

var opts = {
    url: 'php/upload.php',
    data: data,
    cache: false,
    contentType: false,
    processData: false,
    method: 'POST',
    type: 'POST', // For jQuery < 1.9
    success: function(data){
        alert(data);
    }
};
if(data.fake) {
    // Make sure no text encoding stuff is done by xhr
    opts.xhr = function() { var xhr = jQuery.ajaxSettings.xhr(); xhr.send = xhr.sendAsBinary; return xhr; }
    opts.contentType = "multipart/form-data; boundary="+data.boundary;
    opts.data = data.toString();
}
jQuery.ajax(opts);

Create FormData from an existing form

Instead of manually iterating the files, the FormData object can also be created with the contents of an existing form object:

var data = new FormData(jQuery('form')[0]);

Use a PHP native array instead of a counter

Just name your file elements the same and end the name in brackets:

jQuery.each(jQuery('#file')[0].files, function(i, file) {
    data.append('file[]', file);
});

$_FILES['file'] will then be an array containing the file upload fields for every file uploaded. I actually recommend this over my initial solution as it’s simpler to iterate over.

Look at my code, it does the job for me

$( '#formId' )
  .submit( function( e ) {
    $.ajax( {
      url: 'FormSubmitUrl',
      type: 'POST',
      data: new FormData( this ),
      processData: false,
      contentType: false
    } );
    e.preventDefault();
  } );

Just wanted to add a bit to Raphael's great answer. Here's how to get PHP to produce the same $_FILES, regardless of whether you use JavaScript to submit.

HTML form:

<form enctype="multipart/form-data" action="/test.php" 
method="post" class="putImages">
   <input name="media[]" type="file" multiple/>
   <input class="button" type="submit" alt="Upload" value="Upload" />
</form>

PHP produces this $_FILES, when submitted without JavaScript:

Array
(
	[media] => Array
		(
			[name] => Array
				(
					[0] => Galata_Tower.jpg
					[1] => 518f.jpg
				)

			[type] => Array
				(
					[0] => image/jpeg
					[1] => image/jpeg
				)

			[tmp_name] => Array
				(
					[0] => /tmp/phpIQaOYo
					[1] => /tmp/phpJQaOYo
				)

			[error] => Array
				(
					[0] => 0
					[1] => 0
				)

			[size] => Array
				(
					[0] => 258004
					[1] => 127884
				)

		)

)

If you do progressive enhancement, using Raphael's JS to submit the files...

var data = new FormData($('input[name^="media"]'));		
jQuery.each($('input[name^="media"]')[0].files, function(i, file) {
	data.append(i, file);
});

$.ajax({
	type: ppiFormMethod,
	data: data,
	url: ppiFormActionURL,
	cache: false,
	contentType: false,
	processData: false,
    success: function(data){
        alert(data);
    }
});

... this is what PHP's $_FILES array looks like, after using that JavaScript to submit:

Array
(
    [0] => Array
        (
            [name] => Galata_Tower.jpg
            [type] => image/jpeg
            [tmp_name] => /tmp/phpAQaOYo
            [error] => 0
            [size] => 258004
        )

    [1] => Array
        (
            [name] => 518f.jpg
            [type] => image/jpeg
            [tmp_name] => /tmp/phpBQaOYo
            [error] => 0
            [size] => 127884
        )

)

That's a nice array, and actually what some people transform $_FILES into, but I find it's useful to work with the same $_FILES, regardless if JavaScript was used to submit. So, here are some minor changes to the JS:

// match anything not a [ or ]
regexp = /^[^[\]]+/;
var fileInput = $('.putImages input[type="file"]');
var fileInputName = regexp.exec( fileInput.attr('name') );

// make files available
var data = new FormData();
jQuery.each($(fileInput)[0].files, function(i, file) {
	data.append(fileInputName+'['+i+']', file);
});

(14 April 2017 edit: I removed the form element from the constructor of FormData() -- that fixed this code in Safari.)

That code does two things.

1. Retrieves the input name attribute automatically, making the HTML more maintainable. Now, as long as form has the class putImages, everything else is taken care of automatically. That is, the input need not have any special name.
2. The array format that normal HTML submits is recreated by the JavaScript in the data.append line. Note the brackets.

With these changes, submitting with JavaScript now produces precisely the same $_FILES array as submitting with simple HTML.

I just built this function based on some info I read.

Use it like using .serialize(), instead just put .serializefiles();.
Working here in my tests.

//USAGE: $("#form").serializefiles();
(function($) {
$.fn.serializefiles = function() {
	var obj = $(this);
	/* ADD FILE TO PARAM AJAX */
	var formData = new FormData();
	$.each($(obj).find("input[type='file']"), function(i, tag) {
		$.each($(tag)[0].files, function(i, file) {
			formData.append(tag.name, file);
		});
	});
	var params = $(obj).serializeArray();
	$.each(params, function (i, val) {
		formData.append(val.name, val.value);
	});
	return formData;
};
})(jQuery);

If your form is defined in your HTML, it is easier to pass the form into the constructor than it is to iterate and add images.

$('#my-form').submit( function(e) {
    e.preventDefault();
    
    var data = new FormData(this); // <-- 'this' is your form element
    
    $.ajax({
            url: '/my_URL/',
            data: data,
            cache: false,
            contentType: false,
            processData: false,
            type: 'POST',     
            success: function(data){
            ...

Devin Venable's answer was close to what I wanted, but I wanted one that would work on multiple forms, and use the action already specified in the form so that each file would go to the right place.

I also wanted to use jQuery's on() method so I could avoid using .ready().

That got me to this: (replace formSelector with your jQuery selector)

$(document).on('submit', formSelecter, function( e ) {
    	e.preventDefault();
	$.ajax( {
		url: $(this).attr('action'),
		type: 'POST',
		data: new FormData( this ),
		processData: false,
		contentType: false
	}).done(function( data ) {
		//do stuff with the data you got back.
	});
	
});

If the file input name indicates an array and flags multiple, and you parse the entire form with FormData, it is not necessary to iteratively append() the input files. FormData will automatically handle multiple files.

$('#submit_1').on('click', function() {
  let data = new FormData($("#my_form")[0]);

  $.ajax({
    url: '/path/to/php_file',
    type: 'POST',
    data: data,
    processData: false,
    contentType: false,
    success: function(r) {
      console.log('success', r);
    },
    error: function(r) {
      console.log('error', r);
    }
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form id="my_form">
  <input type="file" name="multi_img_file[]" id="multi_img_file" accept=".gif,.jpg,.jpeg,.png,.svg" multiple="multiple" />
  <button type="button" name="submit_1" id="submit_1">Not type='submit'</button>
</form>

Note that a regular button type="button" is used, not type="submit". This shows there is no dependency on using submit to get this functionality.

The resulting $_FILES entry is like this in Chrome dev tools:

multi_img_file:
  error: (2) [0, 0]
  name: (2) ["pic1.jpg", "pic2.jpg"]
  size: (2) [1978036, 2446180]
  tmp_name: (2) ["/tmp/phphnrdPz", "/tmp/phpBrGSZN"]
  type: (2) ["image/jpeg", "image/jpeg"]

Note: There are cases where some images will upload just fine when uploaded as a single file, but they will fail when uploaded in a set of multiple files. The symptom is that PHP reports empty $_POST and $_FILES without AJAX throwing any errors. Issue occurs with Chrome 75.0.3770.100 and PHP 7.0. Only seems to happen with 1 out of several dozen images in my test set.

Nowadays you don't even need jQuery:) fetch API support table

let result = fetch('url', {method: 'POST', body: new FormData(document.querySelector("#form"))})

The FormData class does work, however in iOS Safari (on the iPhone at least) I wasn't able to use Raphael Schweikert's solution as is.

Mozilla Dev has a nice page on manipulating FormData objects.

So, add an empty form somewhere in your page, specifying the enctype:

<form enctype="multipart/form-data" method="post" name="fileinfo" id="fileinfo"></form>

Then, create FormData object as:

var data = new FormData($("#fileinfo"));

and proceed as in Raphael's code.

One gotcha I ran into today I think is worth pointing out related to this problem: if the url for the ajax call is redirected then the header for content-type: 'multipart/form-data' can be lost.

For example, I was posting to http://server.com/context?param=x

In the network tab of Chrome I saw the correct multipart header for this request but then a 302 redirect to http://server.com/context/?param=x (note the slash after context)

During the redirect the multipart header was lost. Ensure requests are not being redirected if these solutions are not working for you.

Older versions of IE do not support FormData ( Full browser support list for FormData is here: https://developer.mozilla.org/en-US/docs/Web/API/FormData).

Either you can use a jquery plugin (For ex, http://malsup.com/jquery/form/#code-samples ) or, you can use IFrame based solution to post multipart form data through ajax: https://developer.mozilla.org/en-US/docs/Learn/HTML/Forms/Sending_forms_through_JavaScript

All the solutions above are looks good and elegant, but the FormData() object does not expect any parameter, but use append() after instantiate it, like what one wrote above:

formData.append(val.name, val.value);

1. get form object by jquery-> $("#id")[0]
2. data = new FormData($("#id")[0]);
3. ok,data is your want