Share page link for social networking sites

gistfile1.php

<?php

$linked_in = 'http://www.linkedin.com/shareArticle?mini=true&url=';

$facebook = 'https://www.facebook.com/sharer/sharer.php?u=';

$twitter = 'https://mobile.twitter.com/home?status=';

$link = $twitter . urlencode('http://www.briangavindiamonds.com/diamonds/diamond-details/0.822-g-vs2-round-diamond-ags-104063637016');

echo $link;