Heartstr is a project mainly written in PHP, it's free.
A simple PHP/jQuery vote counter
Heartstr adds heart to any page
Requires: MySQL, PHP, jQuery
Place heartstr.php at /, create a table and configure it to talk to your MySQL database as instructed in the file.
Copy the contents of heartstr-min.html into your site template on location where you want the heart to be displayed, or grab the source from index.html if you wish to customize.
Creative Commons Attribution 3.0 Unported License http://creativecommons.org/licenses/by/3.0/