PHP AJAX Image Uploading with FormData

Question

I am relatively new to jQuery and Ajax functions, but have been working with Ajax forms over the past few days. I have come to a problem with file uploads however when trying to upload images. Whilst looking for resources, I couldn't find anything useful because they seem to be over-complicated with pointless extras or have no explanation whatsoever, which doesn't help me to learn any further.

I have wrote this code to handle the image upload in Ajax:

$(function() {
    $('.input_photo').on("change",function() {                              
        var formData = new FormData($('form.upload-form'));

        $.ajax({
            url: "upload.php",
            type: "POST",
            data: formData,
            success: function (msg) {
                alert(msg)
            }
        });
    });
});

This sends a request to the upload.php file, however no data is sent, basically my form is literally this:

<form class="upload-form">
     <input type="file" name="input_photo" class="input_photo" />
</form>

No data seems to be passed in the headers whatsoever and I assume I would access it through PHP with $_POST['data'] array or $_FILES? Someone with better knowledge please help to explain this, it'd be great to understand this further. Thanks.

Answer 1

This will work for one or multiple files.

$('input:file').on('change', function () {  

 var data = new FormData();

 //Append files infos
 jQuery.each($(this)[0].files, function(i, file) {
     data.append('file-'+i, file);
 });

 $.ajax({  
     url: "my_path",  
     type: "POST",  
     data: data,  
     cache: false,
     processData: false,  
     contentType: false, 
     context: this,
     success: function (msg) {
          alert(msg);
      }
  });
});

Then

$_FILES['file-0']
$_FILES['file-1']
[...]

But be careful that using FormData doesn't work on IE before IE10