diff --git a/contrib/ban_words/main.php b/contrib/ban_words/main.php
index 840c198c..aee98417 100644
--- a/contrib/ban_words/main.php
+++ b/contrib/ban_words/main.php
@@ -19,11 +19,10 @@
  *  from Essex"
  */
 
-class BanWords implements Extension {
-	public function receive_event(Event $event) {
-		if($event instanceof InitExtEvent) {
-			global $config;
-			$config->set_default_string('banned_words', "
+class BanWords extends SimpleExtension {
+	public function onInitExt(InitExtEvent $event) {
+		global $config;
+		$config->set_default_string('banned_words', "
 a href=
 anal
 blowjob
@@ -50,42 +49,42 @@ ultram
 very nice site
 viagra
 xanax
-			");
-		}
+");
+	}
 
-		if($event instanceof CommentPostingEvent) {
-			global $config;
-			$banned = $config->get_string("banned_words");
-			$comment = strtolower($event->comment);
+	public function onCommentPosting(CommentPostingEvent $event) {
+		global $config;
+		$banned = $config->get_string("banned_words");
+		$comment = strtolower($event->comment);
 
-			foreach(explode("\n", $banned) as $word) {
-				$word = trim(strtolower($word));
-				if(strlen($word) == 0) {
-					// line is blank
-					continue;
+		foreach(explode("\n", $banned) as $word) {
+			$word = trim(strtolower($word));
+			if(strlen($word) == 0) {
+				// line is blank
+				continue;
+			}
+			else if($word[0] == '/') {
+				// lines that start with slash are regex
+				if(preg_match($word, $comment)) {
+					throw new CommentPostingException("Comment contains banned terms");
 				}
-				else if($word[0] == '/') {
-					// lines that start with slash are regex
-					if(preg_match($word, $comment)) {
-						throw new CommentPostingException("Comment contains banned terms");
-					}
-				}
-				else {
-					// other words are literal
-					if(strpos($comment, $word) !== false) {
-						throw new CommentPostingException("Comment contains banned terms");
-					}
+			}
+			else {
+				// other words are literal
+				if(strpos($comment, $word) !== false) {
+					throw new CommentPostingException("Comment contains banned terms");
 				}
 			}
 		}
-
-		if($event instanceof SetupBuildingEvent) {
-			$sb = new SetupBlock("Banned Phrases");
-			$sb->add_label("One per line, lines that start with slashes are treated as regex<br/>");
-			$sb->add_longtext_option("banned_words");
-			$event->panel->add_block($sb);
-		}
 	}
+
+	public function onSetupBuilding(SetupBuildingEvent $event) {
+		$sb = new SetupBlock("Banned Phrases");
+		$sb->add_label("One per line, lines that start with slashes are treated as regex<br/>");
+		$sb->add_longtext_option("banned_words");
+		$event->panel->add_block($sb);
+	}
+
+	public function get_priority() {return 30;}
 }
-add_event_listener(new BanWords(), 30); // before the comment is added
 ?>
diff --git a/contrib/image_hash_ban/main.php b/contrib/image_hash_ban/main.php
index eee5d6d7..292a9da6 100644
--- a/contrib/image_hash_ban/main.php
+++ b/contrib/image_hash_ban/main.php
@@ -30,27 +30,32 @@ class AddImageHashBanEvent extends Event {
 }
 // }}}
 class ImageBan implements Extension {
-	var $theme;
+	public function onInitExt(InitExtEvent $event) {
+		global $config, $database;
+		if($config->get_int("ext_imageban_version") < 1) {
+			$database->create_table("image_bans", "
+				id SCORE_AIPK,
+				hash CHAR(32) NOT NULL,
+				date DATETIME DEFAULT SCORE_NOW,
+				reason TEXT NOT NULL
+			");
+			$config->set_int("ext_imageban_version", 1);
+		}
+	}
 
-	public function receive_event(Event $event) {
+	public function onDataUpload(DataUploadEvent $event) {
+		global $database;
+		$row = $database->db->GetRow("SELECT * FROM image_bans WHERE hash = ?", $event->hash);
+		if($row) {
+			log_info("image_hash_ban", "Blocked image ({$event->hash})");
+			throw new UploadException("Image ".html_escape($row["hash"])." has been banned, reason: ".format_text($row["reason"]));
+		}
+	}
+
+	public function onPageRequest(PageRequestEvent $event) {
 		global $config, $database, $page, $user;
-		if(is_null($this->theme)) $this->theme = get_theme_object($this);
 
-		if($event instanceof InitExtEvent) {
-			if($config->get_int("ext_imageban_version") < 1) {
-				$this->install();
-			}
-		}
-
-		if($event instanceof DataUploadEvent) {
-			$row = $database->db->GetRow("SELECT * FROM image_bans WHERE hash = ?", $event->hash);
-			if($row) {
-				log_info("image_hash_ban", "Blocked image ({$event->hash})");
-				throw new UploadException("Image ".html_escape($row["hash"])." has been banned, reason: ".format_text($row["reason"]));
-			}
-		}
-
-		if(($event instanceof PageRequestEvent) && $event->page_matches("image_hash_ban")) {
+		if($event->page_matches("image_hash_ban")) {
 			if($user->is_admin()) {
 				if($event->get_arg(0) == "add") {
 					if(isset($_POST['hash']) && isset($_POST['reason'])) {
@@ -87,38 +92,28 @@ class ImageBan implements Extension {
 				}
 			}
 		}
+	}
 
-		if($event instanceof UserBlockBuildingEvent) {
-			if($user->is_admin()) {
-				$event->add_link("Image Bans", make_link("image_hash_ban/list/1"));
-			}
-		}
-
-		if($event instanceof AddImageHashBanEvent) {
-			$this->add_image_hash_ban($event->hash, $event->reason);
-		}
-
-		if($event instanceof RemoveImageHashBanEvent) {
-			$this->remove_image_hash_ban($event->hash);
-		}
-
-		if($event instanceof ImageAdminBlockBuildingEvent) {
-			if($user->is_admin()) {
-				$event->add_part($this->theme->get_buttons_html($event->image));
-			}
+	public function onUserBlockBuilding(UserBlockBuildingEvent $event) {
+		global $user;
+		if($user->is_admin()) {
+			$event->add_link("Image Bans", make_link("image_hash_ban/list/1"));
 		}
 	}
 
-	protected function install() {
-		global $database;
-		global $config;
-		$database->create_table("image_bans", "
-			id SCORE_AIPK,
-			hash CHAR(32) NOT NULL,
-			date DATETIME DEFAULT SCORE_NOW,
-			reason TEXT NOT NULL
-		");
-		$config->set_int("ext_imageban_version", 1);
+	public function onAddImageHashBan(AddImageHashBanEvent $event) {
+		$this->add_image_hash_ban($event->hash, $event->reason);
+	}
+
+	public function onRemoveImageHashBan(RemoveImageHashBanEvent $event) {
+		$this->remove_image_hash_ban($event->hash);
+	}
+
+	public function onImageAdminBlockBuilding(ImageAdminBlockBuildingEvent $event) {
+		global $user;
+		if($user->is_admin()) {
+			$event->add_part($this->theme->get_buttons_html($event->image));
+		}
 	}
 
 	// DB funness
@@ -145,6 +140,7 @@ class ImageBan implements Extension {
 		$database->Execute("DELETE FROM image_bans WHERE hash = ?", array($hash));
 	}
 
+	// in before resolution limit plugin
+	public function get_priority() {return 30;}
 }
-add_event_listener(new ImageBan(), 30); // in before resolution limit plugin
 ?>
diff --git a/ext/handle_404/main.php b/ext/handle_404/main.php
index f5baf731..3a9a2503 100644
--- a/ext/handle_404/main.php
+++ b/ext/handle_404/main.php
@@ -8,20 +8,18 @@
  * Description: Shows an error message when the user views a page with no content
  */
 
-class Handle404 implements Extension {
-	public function receive_event(Event $event) {
-		if($event instanceof PageRequestEvent) {
-			global $page;
-			// hax.
-			if($page->mode == "page" && (!isset($page->blocks) || $this->count_main($page->blocks) == 0)) {
-				$h_pagename = html_escape(implode('/', $event->args));
-				header("HTTP/1.0 404 Page Not Found");
-				log_debug("handle_404", "Hit 404: $h_pagename");
-				$page->set_title("404");
-				$page->set_heading("404 - No Handler Found");
-				$page->add_block(new NavBlock());
-				$page->add_block(new Block("Explanation", "No handler could be found for the page '$h_pagename'"));
-			}
+class Handle404 extends SimpleExtension {
+	public function onPageRequest(PageRequestEvent $event) {
+		global $page;
+		// hax.
+		if($page->mode == "page" && (!isset($page->blocks) || $this->count_main($page->blocks) == 0)) {
+			$h_pagename = html_escape(implode('/', $event->args));
+			header("HTTP/1.0 404 Page Not Found");
+			log_debug("handle_404", "Hit 404: $h_pagename");
+			$page->set_title("404");
+			$page->set_heading("404 - No Handler Found");
+			$page->add_block(new NavBlock());
+			$page->add_block(new Block("Explanation", "No handler could be found for the page '$h_pagename'"));
 		}
 	}
 
@@ -32,6 +30,7 @@ class Handle404 implements Extension {
 		}
 		return $n;
 	}
+
+	public function get_priority() {return 99;}
 }
-add_event_listener(new Handle404(), 99); // hax++
 ?>
diff --git a/ext/upgrade/main.php b/ext/upgrade/main.php
index dcadb884..30722eef 100644
--- a/ext/upgrade/main.php
+++ b/ext/upgrade/main.php
@@ -6,14 +6,8 @@
  * Visibility: admin
  */
 
-class Upgrade implements Extension {
-	public function receive_event(Event $event) {
-		if($event instanceof InitExtEvent) {
-			$this->do_things();
-		}
-	}
-
-	private function do_things() {
+class Upgrade extends SimpleExtension {
+	public function onInitExt(InitExtEvent $event) {
 		global $config, $database;
 
 		if(!is_numeric($config->get_string("db_version"))) {
@@ -36,8 +30,6 @@ class Upgrade implements Extension {
 			log_info("upgrade", "Database at version 7");
 		}
 
-		// TODO:
-		// add column image->locked
 		if($config->get_int("db_version") < 8) {
 			// if this fails, don't try again
 			$config->set_int("db_version", 8);
@@ -47,6 +39,7 @@ class Upgrade implements Extension {
 			log_info("upgrade", "Database at version 8");
 		}
 	}
+
+	public function get_priority() {return 5;}
 }
-add_event_listener(new Upgrade(), 5);
 ?>
diff --git a/ext/view/main.php b/ext/view/main.php
index f4da7507..f0f42ae2 100644
--- a/ext/view/main.php
+++ b/ext/view/main.php
@@ -66,17 +66,15 @@ class ImageAdminBlockBuildingEvent extends Event {
 	}
 }
 
-class ViewImage implements Extension {
-	var $theme;
+class ViewImage extends SimpleExtension {
+	public function onPageRequest(PageRequestEvent $event) {
+		global $page;
 
-	public function receive_event(Event $event) {
-		global $config, $database, $page, $user;
-		if(is_null($this->theme)) $this->theme = get_theme_object($this);
-
-		if(is_a($event, 'PageRequestEvent') && (
+		if(
 			$event->page_matches("post/prev") ||
 			$event->page_matches("post/next")
-		)) {
+		) {
+
 			$image_id = int_escape($event->get_arg(0));
 
 			if(isset($_GET['search'])) {
@@ -105,7 +103,7 @@ class ViewImage implements Extension {
 			}
 		}
 			
-		if(($event instanceof PageRequestEvent) && $event->page_matches("post/view")) {
+		if($event->page_matches("post/view")) {
 			$image_id = int_escape($event->get_arg(0));
 
 			$image = Image::by_id($image_id);
@@ -122,7 +120,7 @@ class ViewImage implements Extension {
 			}
 		}
 
-		if(($event instanceof PageRequestEvent) && $event->page_matches("post/set")) {
+		if($event->page_matches("post/set")) {
 			$image_id = int_escape($_POST['image_id']);
 
 			send_event(new ImageInfoSetEvent(Image::by_id($image_id)));
@@ -131,14 +129,13 @@ class ViewImage implements Extension {
 			$page->set_mode("redirect");
 			$page->set_redirect(make_link("post/view/$image_id", $query));
 		}
+	}
 
-		if($event instanceof DisplayingImageEvent) {
-			$iibbe = new ImageInfoBoxBuildingEvent($event->get_image(), $user);
-			send_event($iibbe);
-			ksort($iibbe->parts);
-			$this->theme->display_page($page, $event->get_image(), $iibbe->parts);
-		}
+	public function onDisplayingImage(DisplayingImageEvent $event) {
+		$iibbe = new ImageInfoBoxBuildingEvent($event->get_image(), $user);
+		send_event($iibbe);
+		ksort($iibbe->parts);
+		$this->theme->display_page($event->get_image(), $iibbe->parts);
 	}
 }
-add_event_listener(new ViewImage());
 ?>
diff --git a/ext/view/theme.php b/ext/view/theme.php
index 05d78386..62ae8204 100644
--- a/ext/view/theme.php
+++ b/ext/view/theme.php
@@ -4,7 +4,9 @@ class ViewImageTheme extends Themelet {
 	/*
 	 * Build a page showing $image and some info about it
 	 */
-	public function display_page(Page $page, Image $image, $editor_parts) {
+	public function display_page(Image $image, $editor_parts) {
+		global $page;
+
 		$metatags = str_replace(" ", ", ", html_escape($image->get_tag_list()));
 
 		$page->set_title("Image {$image->id}: ".html_escape($image->get_tag_list()));