Auto-login system using php curl for a few sites

Project Description:
I sell books on the internet on the following sites

amazon.co.uk
abebooks.co.uk
biblio.co.uk
alibris.co.uk

I have created a crawler which scrapes websites for sales reports but unfortunately I do not know how to login to sites using php curl.

Here is an example of a php function which can log in to facebook and redirects to facebook's homepage (this function works).

function facebookLogin(){
$login_email = 'email;
$login_pass = 'pass';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://www.facebook.com/login.php');
curl_setopt($ch, CURLOPT_POSTFIELDS,'email='.urlencode($login_email).'&pass='.urlencode($login_pass).'&login=Login');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_COOKIEJAR, "cookies.txt");
curl_setopt($ch, CURLOPT_COOKIEFILE, "cookies.txt");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.3) Gecko/20070309 Firefox/2.0.0.3");
curl_setopt($ch, CURLOPT_REFERER, "http://www.facebook.com");
$page = curl_exec($ch);
echo $page;
}

what I want is functions for amazon.co.uk, abebooks.co.uk, biblio.co.uk and alibris.co.uk which can do the same thing as the facebookLogin function, for an experienced person this should be an easy job. Thank you