Here is self-explanatory PHP function that will help you to generate Social Sharing links easily.

function share($to, $title, $url)
{
	$url = urlencode($url);
	$title = urlencode($title);

	switch ($to) {
		case 'facebook':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://www.facebook.com/share.php?u=$url&title=$title\" ";
			break;

		case 'twitter':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://twitter.com/home?status=$title+$url\" ";
			break;

		case 'google+':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"https://plus.google.com/share?url=$url\" ";
			break;

		case 'tumblr':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://www.tumblr.com/share?v=3&u=$url&t=$title\" ";
			break;
		
		case 'pintrest':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://pinterest.com/pin/create/bookmarklet/?url=$url&is_video=false&description=$title\" ";
			break;

		case 'linkedin':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://www.linkedin.com/shareArticle?mini=true&url=$url&title=$title\" ";
		break;

		case 'reddit':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://www.reddit.com/submit?url=$url&title=$title\" ";
		break;
		
		case 'stumbleupon':
			return " 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;\" href=\"http://www.stumbleupon.com/submit?url=$url&title=$title\" ";
		break;
		default:
			return "";
			break;
	}
}

To use it, just call the the function with appropriate params

echo share("facebook", "Page Title", "http://page.com/link.html");