Niccolò,
There's a few options for doing that. First, you can use any of the methods in the common support area for a custom login button. These will, when clicked by a logged in user, map their Facebook account to the currently logged in Joomla user. For more information on the custom login buttons, see:
www.sourcecoast.com/jfbconnect/docs/common-support-questions
For the standard 'blue button', you can use the following code (which is what we use in the JFBCLogin module):
<fb:login-button v="2" onlogin="javascript:jfbc.login.login_button_click();">Reconnect Account</fb:login-button>
Finally, to make sure that the user isn't already logged into an account that's mapped to a Facebook account, you'll want to use the following PHP code to check:
require_once JPATH_ROOT.DS.'components'.DS.'com_jfbconnect'.DS.'libraries'.DS.'facebook.php';
$jfbcLibrary = JFBConnectFacebookLibrary::getInstance();
$fbId = $jfbcLibrary->getMappedFbUserId();
if (!$fbId)
echo '<fb:login-button v="2" onlogin="javascript:jfbc.login.login_button_click();">Reconnect Account</fb:login-button>';
Hope that helps, but if you have any other questions, just let us know.
Thanks,
Alex
"connect with facebok" option in login form
