CodeCanyon - Viral Lock PHP - Like, Google+1 or Tweet to Unlock | 171 KB
Make your site go viral by requiring your users to Facebook Like, Google+1 or Tweet about your page to reveal premium content. Simply wrap the content you want to protect with the script and your content will be protected until the users shares your page. Viral-Lock is the first of its kind to combine Facebook, Google+ and Twitter to give maximal viral impact. More likes and tweets = More money for you.
Based on our Viral Lock plugin for WordPress the PHP version enables you to integrate the power of Viral Lock into anything. Anything you can put in a PHP file can be protected!
DEMO:
http://codecanyon.net/item/viral-lock-php-like-google1-or-tweet-to-unlock/1632879