You can use below PHP script to add Facebook LIKE button to your website :
// Display facebook LIKE button
echo "<br><iframe scrolling=\"no\"
src=\"http://www.facebook.com/plugins/like.php?href=";
echo 'http://'.$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'];
echo "&layout=standard&show_faces=false&width=450&action=like&colorscheme=light\"
frameborder=\"0\" style=\"border: none; overflow: hidden; height: 35px;
margin-top: 10px; margin-bottom: 0px;\"></iframe>" ;