[Simon Lloyd]

So something like (inside body tag)

<div id="fb-root"></div>

<script>
(function(d, s, id) {
  
var js, fjs = d.getElementsByTagName(s)[0];
  
if (d.getElementById(id)) return;
  
js = d.createElement(s); 
js.id = id;
  
js.src = "//connect.facebook.net/en_GB/sdk.js#xfbml=1&version=v2.0";
  
fjs.parentNode.insertBefore(js, fjs);

}
(document, 'script', 'facebook-jssdk'));
</script>

Below goes Where you want the button to appear

<div class="fb-share-button" data-href="/showthread.php?$session[sessionurl]t=$thread[threadid]" data-width="The pixel width of the plugin" data-type="button"></div>

you can change the url...etc in the above.