Validate a Facebook page URL

Question

For an application I am developing, we allow users to add a link to their Facebook Page (strictly page, not Profile, not Group, only a Page).

I cannot find anything

Answer 1

I needed something that checked to see if it was a valid Page or Group. My user submits a text field which comes via $_POST as $_POST['mu_facebook']

if(class_exists('Facebook')){   
        $facebook = new Facebook(array(
         'appId'  => 'yourapplicationID',
         'secret' => 'yoursecretcode',
         'cookie' => true,
        ));

       //break up the saved URL to see what we're dealing with
    $parts = explode('/', $_POST['mu_facebook']); 
    if($key = array_search('groups', $parts)) 
        $query = $parts[$key+1]; //if this is a group URL, the ID will be in the next key after /group/
    else
        $query = $_POST['mu_facebook'];

    try {
        $fb_data = $facebook->api($query);
    } catch (FacebookApiException $e){
        //insert your own error here - Facebook did not recognize this object (group id failures will happen here)
    }
    //If FB doesn't recognize the URL, the API simply shows the requested URL as the id or returns an object wth type = 'website' (Page URL failures will happen here)
    if($fb_data["id"] && $fb_data["id"] !== $_POST['mu_facebook'] && $fb_data["type"] !== "website"){
        //We have a valid URL
        update_as_site_option('mu_facebook');
    } else {
        //insert your own error here - Facebook did not recognize this object
    }
}