PHP Securimage captcha bypass

This concerns sites using PHP Securimage technology for their captchas (see [login to view URL] - example site using it at [login to view URL]). I need a way of grabbing the image shown - doing a View Image for the example site above gives the [login to view URL] URL, though reloading always shows a different image - and understanding how Securimage works in terms of checking whether the user has entered the right text or not. It's something to do with the session cookie, so perhaps Securimage stores what the correct text should be against the session cookie in a database on the site, I'm unsure. I'm looking for: (a) a way to grab a static image so it can be passed on to someone to solve, and (b) an understanding of what has to be passed back through the form to make it work okay and validate properly. Please note the solution should NOT involve needing to load the page in a normal browser, and using some kind of javascript to grab the image - I have scripts calling pages using PHP CURL that this solution needs to fit into, so I need to be able to programmatically grab the static image, and know what I need to send back when I programmatically submit the form so that it validates the solves captcha okay.