I saw an article here: http://code.lancepollard.com/automatically-publish-posts-to-stumbleupon-with-ruby
I don’t know Ruby, but the following lines are pretty self explanatory:
page = agent.get("http://www.stumbleupon.com/submit?url=#{url}&title=#{title}")
form = page.forms.first
form.radiobuttons_with(:name => "sfw").first.check
page = agent.submit(form)
I’m guessing Ruby can fetch the webpage, check a checkbox, then submit the form. Is that possible using PHP?
The Ruby code you referenced actually uses a third party library called Mechanize.
Something similar for PHP is The SimpleTest Scriptable Browser. It’s not as feature rich as Mechanize but can get the job done and it can be used independently of the SimpleTest framework.