add and check plugin base class

classes/plugin.php

@@ -0,0 +1,11 @@
+<?php
+class Plugin {
+	private $link;
+	private $host;
+
+	function __construct($host) {
+		$this->link = $host->get_link();
+		$this->host = $host;
+	}
+}
+?>

classes/pluginhost.php

@@ -59,7 +59,7 @@ class PluginHost {
 
 			if (file_exists($file)) require_once $file;
 
-			if (class_exists($class)) {
+			if (class_exists($class) && is_subclass_of($class, "Plugin")) {
 				$plugin = new $class($this);
 
 				$this->register_plugin($class, $plugin);

plugins/flattr/flattr.php

@@ -1,5 +1,5 @@
 <?php
-class Flattr {
+class Flattr extends Plugin {
 	private $link;
 	private $host;
 

plugins/googleplus/googleplus.php

@@ -1,5 +1,5 @@
 <?php
-class GooglePlus {
+class GooglePlus extends Plugin {
 	private $link;
 	private $host;
 

plugins/identica/identica.php

@@ -1,5 +1,5 @@
 <?php
-class Identica {
+class Identica extends Plugin {
 	private $link;
 	private $host;
 

plugins/mail/mail.php

@@ -1,5 +1,5 @@
 <?php
-class Mail {
+class Mail extends Plugin {
 
 	private $link;
 	private $host;

plugins/note/note.php

@@ -1,5 +1,5 @@
 <?php
-class Note {
+class Note extends Plugin {
 	private $link;
 	private $host;
 

plugins/pinterest/pinterest.php

@@ -1,5 +1,5 @@
 <?php
-class Pinterest {
+class Pinterest extends Plugin {
 	private $link;
 	private $host;
 

plugins/pocket/pocket.php

@@ -1,5 +1,5 @@
 <?php
-class Pocket {
+class Pocket extends Plugin {
 
 	private $link;
 	private $host;

plugins/redditimgur/redditimgur.php

@@ -1,5 +1,5 @@
 <?php
-class RedditImgur {
+class RedditImgur extends Plugin {
 
 	private $link;
 	private $host;

plugins/share/share.php

@@ -1,5 +1,5 @@
 <?php
-class Share {
+class Share extends Plugin {
 	private $link;
 	private $host;