is there a reason you don't want both steps to be taken care of at the same time? I would consider making the upload and the text part of the same form. Make both parts required, and you'll only need one submit button.
you can, however, use multiple submit buttons in PHP. you could make the first one (the picture upload) set a session variable and then redirect to the same page after submission. have your form page then check for the session variable and allow the submission of the 2nd form.
it would be better, i think, to use one form, though.
