File uploads can be done over AJAX (as of xhr2 - if you need to support older browsers, use something like jQuery-File-Upload; there is a good tutorial here on using it just to do the upload part, and not using Blueimp's UI.) That is related to the "without manually submitting the form" part of your question. You will still need to interact with a file upload element to choose the file, and that is where you use page.uploadFile()
.
To do it solely from JavaScript, without "interacting with any element on the page", you could use page.evaluate() to run some custom JavaScript. It could then use the File Reader API to find the file on local disk, store it in a blob, then upload that blob over AJAX. The WebKit in PhantomJS (roughly equivalent to Chrome 13) should work, as apparently the FileReader API has been there since Chrome 6.
(BTW, if all you wanted to do is upload a file to a server using a headless script, PhantomJS is overkill, and you could use curl
. But I'm assuming you want to use PhantomJS for some other reason!)