使用php上传多个文件而不覆盖以前的选择

Question

I am using the upload multiple files example here.

http://davidwalsh.name/multiple-file-upload

Which I have got to work fine, but is there a way to make it behave more like wetransfer(https://www.wetransfer.com/) as in you can keep adding files to upload without actually saving (unsure how wetranser does it).

I know you could keep submitting but I want to get a list of files before submitting so we are not storing unused files on the server e.g. storing them in temp first.

Is this possible?

Currently I have this:

<label for="filesToUpload">Choose your artwork</label>
<input type="file" name="artwork_file[]" id="filesToUpload" multiple="multiple" onchange="makeFileList();"/>

    function makeFileList() {
        //get the input
        var input = document.getElementById('filesToUpload');

        //for every file...
        var list_of_files = "";
        for (var x = 0; x < input.files.length; x++) {
            //add to list
            list_of_files += '<div class="single_uploaded_file"><span>'+input.files[x].name+'</span></div><!--.single_uploaded_file-->';
        }
        jQuery('#file_list').html(list_of_files);
    }